1. A copolymer containing a repeating unit represented by the following formula ( IL ) , and at lea_st one of a repeating unit represented by the folXowing formula. (2-1) and a repeating unit represented by the following forπuαla (2-2) : Formula (1)

wherein R 1
and R 2
represent an alkyl group or an aryl group, provided that at least one of R 1
and R 2
contains a fluorrine atom and R 1
and R 2
are not an alkyl group containing a group represented by -(CX 2
) n
~X in. which X is a halogen atom and n is an integer of 7 or more, Formula (2-1.)

2. The copolymer according "to claim 1, containing tine repeating unit represented by the fiormula (1) wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryL group containing a f luorine atom, and the repeating unit represented by the .formula (2-1) .

3. The copolymer according "
to claim 1, containing ttie repeating unit represented by the fformula (1) wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, and the repeating unz±t represented by the formula (2-1 ) .

4. The copolymer according to claim 2 orr 3, wherein R 3
and. R 4
in the formuILa (2-1) are a methyl group.

5. The copolymer according to any one of claims 1 to -4, containing the repeating unit repnresented by t3ne formula (H) and the repeating un.it represented by the formula (2-1) in a.n amount of 30 mol% o_r more, respectively.

6. The copolymer according to claim 1, (containing ttie repeating unit represented by the formula (1) and the repeating unit represented by the formula ( 2-2) .

7. The copolymer according to claim 1, containing ttie repeating unit represented by the formula (1) , the repeatiang unit represented by the formula (2-1) and the .repeating unzLt represented by the formula (2-2).

8. The copolymer according to claim 7, containing 20 moIL% or more of the repeating unit represented by the formula (1 ) , 0. O5 moll or more of the repeating unit represented by tine foimula (2-2) , and 20 mol% or itLore of the rrepeating un_±t represented by the formula (2-1) .

9. The copolymer according to any one of claims 6 to 8, wherein at least one of R 1
and R 2
in_ the formula (1) is an alk^yl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containing a fluori_ne atom.

10. The copolymer according to any one of claims 1
7 to 9,

wherein R 3
and R 4
in the formula (2-1) are a methyl group.

11. The copolymer according to any one of claims 1 to 10, having a number average molecular weigh t (Mn) of from. 1,000 to 1,000,000.

12. The copolymer according to any one of claims 1 to 11, having a weight average molecular weight (Mw) of from. 2,000 to 1,000,000.

13. The copolymer according to any one of claims 1 to 12, having Mw/Mn of 2 or less .

14. A polymerizable composition containing a compound represented by the following formula ( 3) and at least one of a compound represented by the following formula ( 4) and a polysiloxane-containing c ompound :

Formula (3)

R 1
O 2
C -CH=CH-CO 2
R 2
wherein R 1
and R 2
represent an alkyl giroup or an aryl group, provided that at least one of R 1
and R 2
contains a f luo xine atom and R 1
and R 2
are not aαn alkyl group containing a group represented by -(CX 2
) n
~X i^n which X is a halogen atom, and n is an integezr of 7 or more, Formula ( A )

15. The polymerizabl_e composition according to claim 14, containing the compound represented by the formula (3 '
) wherein at least one of R 1
and R 2
is an alkyl group having ifrom 2 to 6 carbon atoms and a f luori_ne atom, or azn aryl group containing a fluorine atom, and the compound represented by the formula (4) .

16. The polymerizable composition according to claim 14, containing the compound represented by the formula (3) wherein at least one of R 1
and R 2
is an alkyL group having from 2 to 6 carbon atoms and a fluorine atom, and the compound represented by the formula (4) .

18. The polymerizable composition according to claim 14, containing the compound represented by the formula (3) , and. the polysiloxane-containing compound.

19. The polymerizable composition according to claim 14, containing the compound represented by the formula (3)^ the compound represented by the formula (4), and the polysiloxane-containing compound.

20. The polymerizable compositi-on according to claim 18 or 19, wherein at l_east one of R 1
and R 2
in the formula (3) is an alkyl group hav:Lng from 2 to 6 cartoon atoms and a fluorine atom, or an aryl group containing a fluorine atom.

21. The polyrαerizable composition according to claim 19 or 20, containing the compound represented by the formul-H (4) wherein R 3
and R 4
i_n the formula (4) are a methyl group .

22. The polymerizable composition according to an^y one of claims 14 to 21, which is a curing polymerizable composition.

23. A curing resin composition containing the copolymer according to any one of claims 1 to 13, and a solvent.

24. A curing resin composition containing the copolymer according to any one of claims 6 to 10, and a solvent.

25. A cured ffilm made from the curing resin composition according to claims 23 or 24.

26. An antire fleet ive film having a low refractive index .Layer comprising a. cured film made from the curing resin composition accord±ng to claim 23 orr 24.

27. A polarizing plate having a polarizer and a protective

film provided on at least one side of the polarizer, the protective film toeing the antire f lective film according to cl_aim 26.

28. An image display having the antiref 1 ective film according to CIa-Lm 26.

29. An optical waveguide containing the copolymer according to any one of claims 1 to 13.

30. An optical waveguide containing a repeating unit represented by the following formula (1) , and a repeating unit represented by trie following formula (2-1) :

Formula (1)

wherein R 1
and R 2
represent an'allkyl group or an aryl group, provided that at ieast one of R 1
and R 2
contains a fluorine atom and R 1
and R 2
are not an alkyl group containing a group represented by -(CX 2
) n
-X in which X is a halogen atom and n is an integer of 7 or more, Formula (2-1)

wherein R 3
represents an alkyl group, an aryl grou_p, an alkoxy group or an amino group, and R 4
represents an aL kyl group.

31. The optical waveguide according to claims 29 or 30, which is an optical fiber.

32. A metliod of producing a copolymer, including polymerizing a compound represented by the following formula

(3) , and at least one of a compound represented by trie following formula (4) and a. polysiloxane-containing compound:

Formula (3 )

R 1
O 2
C-CH= CH-CO 2
R 2
wherein R 1
and R 2
represent an alkyl group or an aryl grroup , provided tha t: at least one off R 1
and R 2
contains a fluorine atom and R 1
and R 2
are not an alkyl group containing a grroup represented by - ( CXa ) n
-X in "which X is a halogen atom and n is an integer o f 7 or more, Formula ( 4 )

wherein R 3
represents an alkyl group, an arryl group, an a]_koxy group or an amino group, and R 4
represents an alkyl group.

33. The method of producing a copolymer according to claim 32, including polymerizing the compound represented by the formula (3) "wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group conta-Lning a fluorine atom, and the compound represented by the formula (4) .

34. The method of producing a copolymer according to claim 32, including polymerizing the compound represented by the formula (3) and the polysiloxane-containdLng compound.

35. The method of producing a copolymer according to claim 32, including polymerizing the compound represented by the formula (3) r
the compound ^represented by -the formula (4) and the polysiloxane-containincj" compound.

Description:

DESCRIPTION

COPOLYMER AND POLYMERI ZABLE- COMPO SITION

FIELD OF THE INVENTION

The present invention relates to a copolymer having narrow molecular weight distribution and excellent mechanical properties, and capable of forming a coating film having a sufficient low reflectivity, its production method, and a polymerizable composition forr forming the polymer. Further, it relates to a polymerizable composition, an optical material (in particular *
, a polymerizatole composition, a curing resin composition, an antiref lective film, a polari zing plate and an image display) , and an optical waveguide (in particular, a plastic optical fiber (POF) ) ,. using the polymer.

BACKGROUND OF THE INVENTION

Polymer materials excellent in low hygroscopic property, transparency and heat resistance are required in the technical field of plas ~
tic optical members, and as one of polymer materials capable of satisfying those, a fumaric acid dialkyl ester polymer is known (for example, JP-A- 62-169807 and J. Macromol. Sci _ , A25(5-7), 537-554 (1988) ) . Fumaric acid dialkyl ester i s a rare monomer that radically polymerizes, even though it is 1,2 disubstituted ethylene, and a polymer obtained therefrom has extremely high heat resistance _ However, there was the disadvantage that its homopolyitier is a polymer that steric hindrance is too high, so that it is difficult to increase a molecular weight (at most about 100,000), and further, it is rigid and is liable to be a rod-shape, so that mechanical strength (for example, tensile strength) is weak, resulting in a brittle polymer.

To improve this disadvantage, a copolymer with an alkyl vinyl ether is proposed ( JP-A-2000-143741) . However,

mechanical strength of the copolymer is not sufficient. Further, an example of a copolymer of a fumaric acid dialkyl ester with a monomer such as styrene or a. crylonitrile j_s reported (Journal of Polymer Science: Part A.: Vol. 30, 1559

(1992) ) , but mechanical strength, hygroscopic property and thie like are not referred to.

On the other hand, an antireflective film generally prevents contrast from decreasing due to reflection of outside light or prevents an image from reflecting, rLn displays such as cathode ray tube displays (CRT) , plasma displays (PDP) , electroluminescence displays ( ELD) and liquid crystal displays

(LCD) , and therefore is provided on the outermost surface of displays in order to reduce reflectivity usd_ng principle of optical interference.

Such an antireflective film can generally be produced by forming a low reflective index layer having" an appropriate thickness and having a refractive index lower than that of a support on the support. To realize a low refractive index, a material having a refractive index as low as possible is desired for the low refractive iLndex layer. Further, trie antireflective film is required to have high mar resistance j_n order to use the same on the outermost surface of a display. For example, in a thin film of about 100 nm, in order to realize high mar resistance, strength of a coating film itself and adhesion to a lower layer are required.

(introducing voids) are known. However, either of those means have the tendency that coating film strength or adhesion at interface decreases, resulting in deterioration of mar resistance, and low refractive index and higti mar resistance were not achieved in combinat '
ion.

As a method of increasing coating film strength, therre is a method of using a fluorine-containing sol gel film as

described ±n JP-A-2002-265866 and JP-A-2002- 317152. In this method, however, there are great restrictions that (1 ) long-term heating is required for curing, and load of production is large; (2) there is no resistance to sapon±f ication liquid (alkali treatment liquid), and in the case of saponif ication treating a plastic film surface, the treatment cannot be carried out after film formation of an antiref lecti~ve film; and the like .

On the other hand, JP- A-ll-189621, JP- A-ll-228631 and JP-A-2O0O-3137O9 describe means of improving mar resistance by introducing a polysiloxane structure in a f luorine-containin <g copolymer to decrease a friction coefficient of coating film surface. This means is effective to improvement of max resistance to a certain extent, but sufficient mar resistance is not obta±ned for coating films lacking in substantial coatin <g film strength and interfacia.1 adhesion.

Further, WO 2004-017105 pamphlet describes means of improving mar resistance by using a fluorine-containing copolymer and inorganic fine particles in combination t o improve costing film strength and interfacisl adhesion. In this means , however, it was found that there is the case that inorganic fine particles are not sufficiently dispersed in a. matrix of the f luorine-conta±ning copolymer, crude density o f inorganic fine particles causes in the coating film, and haze rises. This problem is particularly problematic in a smooth surface lo-w reflective film having no antiglare property.

Further, plastic optical members have trie advantage that production and processing arre easy, and other advantages, as compared with quartz-based optical members having the same structure, and various applications such as optical waveguide s are recently attempted. In particular, plast±c optical fiber s (POF) have the disadvantage that because element wires are all constituted of a plastic, transmission loss is relatively larg ~
e as compared with quartz types r
but have the advantages that they

have good flexibility,. are lightweight, have good proces sability, and are easily produced as fibers having large bore diameter as compared with quartz-based optical fibers. As materials for optical fibers, polymethyl methacrylate

(PMMA) that is inexpensive and is easily processed is widely used. However, because of a polymer having high water absorbing properrty, the polymer has poor moisture resistance and can only be used in the limited uses. As means to improve moisture resistance, it is an effective means to introduce fluorine atoms . However, it is difficult "to establish high, glass transition temperrature (Tg), that is, heat resistance, i n combination with the moisture resistance. For example, poly (2 , 2, 2-trifluoroethyl methacrylate) in which methyl groups in side chains of PMMA are merely changed f luorine-containing alkyl groups decreases Tg, and POF using this has very poor heat resistance. One of means to solve this problem is all fluorine pol_ymer (TEFLON, registered trademark, AF amorphous f luoropolymer, John Scheires, 1997, Modern Fluoropolymers, p397-398, John Willwy & Sons Ltd.) , and this is an excellent material satisfying various performances suoh as heat resistance, low hygroscopic property, low transmission loss and the like. However, synthesis of a perf luorinated

(diene ) monomer that is a raw material of this polymer is very complicated, and there is the problem that cost of a polymer is hicph.

SUMMARY OF THE INVENTION

λ first object of the invention is to pxovide a copolymer that maintains heat resistance possessed by a fumarate structure, is made to have low hygroscopic property toy introducing fluorine atoms , has excellent mechanical strength, and aíLso has excellent transparency.

A second object of the invention Is to provide the copolymer having excellent antireflective film formation, that

can form a coating film having a sufficient low ref lectivity .

Further, a third object of the invention is to provide an antiref lective film having improved rτiar resistance while maintaining sufficient: antiref lectivity _ In particular, "
the object is to provide a polarizing plate orr a display using siαch an antiref lective film.

A fourth object of the invention is "to provide an optical waveguide being flexible and having low transmission loss, particularly an optical fiber (POF), by using a polymer excellent in all off low hygroscopic property (moisture resistance), heat resistance (high Tg) , mechanical strength (elastic modulus and tensile strength) and transparency, and that can easily be produced.

Specifically, means for solving thte above problems are as follows.

1. A copolymer containing a repeating unit represented by the following formula (1) , and at least one of a repeating unit represented by the following formula (2-1) and a repeating unit represented by the following formuILa (2-2) . Formula (1)

In the formula (1), R 1
and R 2
represent an alkyl group or an aryl group, provided that at least one of R 1
and R 2
contains a fluorine atom and R 1
and R 2
are not an aILkyl group containing a group represented by -(CXa) n
-X in which X is a halogen atom and n is an integer of 7 or more. Formula (2-1)

In the formula (2-1 ) , R 3
represents an alkyl group, an ary]_ group, an alkoxy group or an amino group (which may be an anilino giroup) , and R 4
represents an alkyl group. Formula (2-2)

In the formula (2-2) , R 5
and R 6
each represent a hydrogen, atom, an alkyl group or an aryl group.

2. The copolymer as described in (1), containing the repeating unit rep .resented by the formula (1) wherein at least one of R 1
and R 2
is an alkyl group 3naving from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containing a f lxiorine atom, and the repeating unit represented by the formula (2-1) .

3. The copolymer as describe: d in (1), containing the repeating unit rep .resented by the f o xmula (1) wherein at least one of R 1
and R 2
is an alkyl group .having from 2 to 6 carbon atoms and a fluorine atom, and the r-epeating unit represented by the formula (2 — 1)

4. The copolymer as described in (2) or (3), wherrein R 3
and R 4
in the formula (2-1) are a methyl group.

5. The copolymer as described in any one of (1) to (4), containing the repeating unit repr&sented by the formula (1) and the repeating unit represented Joy the formula (2-1) in an amount of 30 mol% or more, respectively.

6. The copolymer as described in (1), containing the repeating unit represented by the forrmula (1) and the repeating unit represented by the formula- (2—2) .

7. The copolymer as described in (1), containing the repeating unit represented by the formula (1), the repeating unit represented fc»y the formula (2- 1) and the repeating unit represented by the formula (2-2) .

8. The copolymer as described in (7) , containing 20 mol%

ojc more of the repeating unit represented by the formula (1) , 0.05 mol% or more of the repeating unit represented by the formula (2-2) , and 20 mol% or more of the repeating unit represented by "the formula (2-1) _

9. The copolymer as described in any one of (6) to (8), wherein at least one of R 1
and R 2
in the formula (1) is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containing a fluorine atom.

10. The copolymer as described in any one of (7) to (9), wherein R 3
and R 4
in the formula (2-1) are a methyl group.

11. The copolymer as described in any one of (1) to (10) , having a number average molecular weight (Mn) of from 1,000 to \, 000,000.

12. The copolymer as described in any one of (1) to (11) , having a weight average molecular "weight (Mw) of from 2,000 to 1, 000,000.

13. The copolymer as described in any one of (1) to (12) , having Mw/Mn of 2 or less.

14. A pol;ymerizable composi-tion containing a compound represented by the following formula (3) , and at least one of a compound represented by the following formula C 4) and a polysiloxane-containing compound.

Formula (3)

R 1
O 2
C-CH=CH-CO 2
R 2

In the formula (3) , R 1
and R 2
represent an alkyl group or an airryl group, provided that at least one of R 1
and R 2
contains a fluorine atom and R 1
and R 2
are not an alkyl group containing a group represented by - (CX 2
) n
-X in which X is a halogen atom and n is an integer of 7 or more. Formula (4)

Xn the formula ( <4 ) , R 3
represents an alkyl group, an- aryl group, an alkoxy group o r an amino group ( which may be an ani JLino group ) , and R 4
represents an alkyl group .

15 . The po lymerizable composition as described in ( 14 ) , containing the c ompound represented by the formula ( 3 ) wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containing a fluorine atom, and the compound represented by the formula

( 4 ) .

16. The polymerizable composition as described in (14) , containing the compound represented by the formula (3) wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, and the compound represented b>y the formula (4) .

17. The polymerizable composition as described in (15) or (16), containing the compound represented by the formula (4) wherein R 3
and R 4
is a methyl giroup.

18. The polymerizable composition as described in (14) , containing the compound represented by the formula (3) , and the polysiloxane-containing compound .

19. The polymerizable composition as described in (14), containing the compound represented by the formula (3), the compound represented by trie formula (4), and the polysiloxane-containing compound .

20. The polymerizable composition as described in (18) or (19), wherein at least one of R 1
and R 2
in the formula (3) is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containing a fluorine atom.

21. The polymerizable composition as described in (19) or (20), containing the compound represented by the formula (4) wherein R 3
and R 4
in the formula (4) are a methyl, group.

22. The polymerizable composition as described in any one of (14) to (21), which is a curing polymerizable composition.

23. A curing resin composition containing tb_e copolymer

as described in any one of (1) to (13) , and a. solvent.

24. A cur- ing resin compos±tion containing the copolymer as described in any one of (6) to (10), and a. solvent.

25. A curred film made from the curing resin composition as described in (23) or (24) .

26. An an-tireflective film having a low refractive index layer comprising a cured film, made from the curing resin composition as described in (23) or (24) .

27. A polarizing plate having a polarizer and a protective film provided on at least one side of the polarizer, the protective film being the antireflective film as described in (26) .

28. An image display havj_ng the antirefILective film as described in (26) .

29. An optical waveguide containing th.e copolymer as described in any one of (1) to (13) .

30. An optical waveguide containing a repeating unit represented by the following forrmula (1), and a repeating unit represented by the following formula (2-1) .

Formula (1)

In the formula (1), R 1
and R 2
represent an alkiyl group or an aryl group, provided that at least one of R 1
and R 2
contains a fluorine atom, and R 1
and R 2
are not an alkyl g_roup containing a group represented by - (CX 2
) n
-X in which X is a halogen atom and n is an integer of 7 or more. Formula (2-1)

In the formula (2-1) , R 3
represents an alkyl groujp, an aryl group, an alkoxy group or an amino group (which may be an anilino group) , and R 4
represents an alkyl group.

31. The optical waveguide as described in (29) or (39) , which is an optical fiber.

32. A method of producing a copolymer, including polymerizing a. compound represented by the fol_ lowing formula

(3) , and at least one of a compound represented by the following formula (4) and a polysiloxane -containing conrpound. Formula (3)

R 1
O 2
C-CH=CH- CO 2
R 2

In the formula (3) , R 1
and R 2
represent an alkiyl group or an aryl group, provided that at least one of R 1
and R 2
contains a fluorine atom and R 1
and R 2
are not an alkyl group containing a group represented by - (CX 2
) n
-2[ in which X is a halogen atom and n is an integer of 7 or more. Formula (4)

In the formula (4) , R 3
represents an alkyl group r
an aryl group, an alkoxy group or an amino group (which may be an anilino group) , and R 4
represents an alkyl group .

33. The method of producing a copolymer as described in (32), including polymerizing tJαe compound represented by the formula (3) wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containzLng a fluorine atom, and the compound represented by the formula. (4) .

34. The method of producing a copolymer as described in (32) , including polymerizing the compound represented by the formula (3) and the polysiloxane-containing compound.

IO

35. The method of producing a copolymer as described in (32), includ-Lng polymerizing the compound represented by the formula (3), the compound represented -by the formula (4) and the polysilo∑cane-containing compound.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described in detail below.

In the present description, the numerical range expressed by the wording "a number to another number" mean s a range that falls between the former number indicating the lowermost limit of the range and the latter number indicating the uppermost limit thereof. Further, the descriptions of "a copolymer containing repeating units A and B", "a copolymer formed by polymerizing monomers A and B", and the like mean that the copolymer may consists of A or B alone, may contain both A and B, or may furrther contain other component.

Further?, in the present de scription, "carbon atom number" in each "group" means the numberr including the number of carbon atoms of substituents where trie group has a sixbstituent .

The copolymer of the invention is described.

The copolymer of the invention is a copolymer containing a repeating unit represented by the following fojcmula (1) , and at least one of a repeating unit represented by the following formula (2-1) and a repeating unit represented by the following formula (2-2) . Formula (1)

In the formu-La ( 1 ) , R 1
and R 2
represent an alkyl group or an aryl group, provided that at "
L east one of R 1
and R 2
contains a fluorine at om and R 1
and R 2
are not an alkyl group containing a group repre sented by - (CX2) n
~X in which X is a halogen atom

i n

and n is an integer of 7 or more. Formula (2-1)

In the formula (2-1) , R 3
represents an alkyl group , an aryl group, an alkoxy group or an amino group (which may be an anilino group) , and R 4
represents an alkyl group. Formula (2-2)

In the formula (2-2) , R and R each "
represent a .hydrogen atom, an alkyl group or an aryl group. (Copolymer: of type A)

A preferable first embodiment of the copolymer of the invention ±s a copolymer (type A) containing the repeating unit represented by the formula. (1) and the repeating unit represented by the formula (2-1) .

In tune formula (1) , R 1
and R 2
each represent an alkyl group or an aryl_ group .

The alkyl group may be any of linear, branched or cyclic form. The alkyl group has preferably from 1 to 10, and more preferably from 1 to 6, carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a benzyl group, and a cyclohexyl group.

On the other hand, the aryl group has preferably from 1 to 8 carbon atoms. Specific examples of the aryl group include a phenyl group and a p-tolyl group.

It i s preferable that at least one of R 1
ancd R 2
is an alkyl

group having from 2 to 6 carbon atoms and a fluorine atom (for example, 2, 2 , 2-trif luoroethyl group,

It is preferable that R 1
and R 2
each arre an alkyl group having from 1 to 6 carbon, atoms, and it is iαor-e preferable that each is a. linear or branched alkyl group having- from 1 to 6 carbon atoms .

As described hereinafter, R 1
and R 2
may be substituted with a substituent, but ±t is preferable that at least one of those is substituted with a fluorine atom.

When R 1
and R 2
a:tre an alkyl group, the alkyl group contain±ng the group represented by -(CXa) n
-X (X is a halogen atom, and n is an integer of 7 or more) is excluded. Where n is more "than 7, crystall±-zability develops, and it becomes not suitable for optical uses.

In a ratio of the total hydrogen atom number and fluorine atom number contained in R 1
and R 2
, it is preferable that the fluorine atom number is half or more of the hydztrogen atom number, and it is more preferable that the fluorine atom number is larger than the hydrogen atom number.

In the formula (2 — 1) , R 3
represents an alkyl group, an aryl group, an alkoxy group or an amino groujp (which may be an anilino group) .

When R 3
is an alkyl group, the alkyl grroup may be any of linear, branched or cyclic form. Linear or cyclic form is preferable, and linear f o xm is more preferable . The alkyl group has preferably from 1 to 6, and more preferably from 1 to 3, carbon atoms . Examples of the preferable al kyl group include a methyl group, an ethyl group, an isopropyl gírroup, a tert -butyl

group r
a cyclohexyl group, a trifluoromethyl group and a penta ±luoroethyl group .

When R 3
is an aryl group, the aryl group preferably has from 6 to 9 carbon atoms , and specific examples thereof include a phenyl group, a pentafluorophenyl group,- a p-tolyl group and a p-crilorophenyl group .

When R 3
is an alkoxy group, the alkoxy group preferably has from 1 to 7 carbon, atoms, and speciffic examples thereof include a methoxy group r
and ethoxy group and a phenyloxy group.

When R 3
is an amino group, the amino group preferably has from 1 to 7 carbon atoms , and specific examples thereof include an N, N-dimethylamino group, a piperidino group and an anilino group .

R 3
is preferably an alkyl group having from 1 to 6 carbon atoms , more preferably a methyl group and a trifluoroemth^ /
1 group, and further preferably a methyl cjroup.

R 4
represents an alkyl group. The alkyl group may be any of linear, branched or cyclic form. Linear or branched foxm is preferable, and linear form is more preferable. The alk;yl group has preferably fitrom 1 to 6, and more preferably from 1 to 3, carbon atoms. Specific examples of the alkyl group include a methyl group,- an ethyl group, an isopropyl group, a tert—butyl group, a cyclohexyl group, a trrifluoromethyl group and SL pentafluoroethyl group. A methyl group is more preferable.

It is preferable that R 3
and R 4
each are an alkyl group, and it is more preferable that R 3
is an alkiyl group having from 1 to 6 carbon atoms, and R 4
is a methyl group.

R 3
and R 4
may be substituted with a substituent, but :±t is preferable that at least one of those is substituted with a fluorine atom.

R 1
to R 4
may further be substituted with a replaceable group . Preferable examples of the sufestituent include a halogen atom (for example, a fluorine atom, a chlorine atom and

a bromine atom, and more preferably fl_uorine atom) , am. alkyl group, an aryl group, a heterocyclic group, a cyano grroup, a hydro:xyl group, a nitrro group, a carboxyl group, an alkoxy group, an aryloxy group, a s ilyloxy group, a hieterocylooxy group, an acyloixy group, a carbomoyloxy group, an silkoxycarbonyloxv group, an arryloxycarbonyloxy group, an amino group (including an anilino group) , an acylamino group, an aminocarbonylamino group, an al koxycarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino grroup, an alkylsuILf onylamino groiαp, an arylsT-ilf onylamino group, a mercapto group, an alkylthio group, an arylthio group, a rietrocyclothoi group, a sulfamoyl group, a sulfo group, an alkylsulf enyl group, an arylsulfenyl group, an alkiylsulfonyl groiαp, an arylsulfonyl group, an acyl group, an aryloxycarbonyl grroup, an alkoxycaroonyl group, a carbamoyl group, an arylazo group, a heterocycloazo group, an imido group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a pho sphinylamino group and a silyl gxoup.

The copolymer of type A contains, for example, the repealling unit repres ented by the formuia (1) and the repeating unit represented by the formula (2-1) in an amount of 1% O-I-: more, respectively, and preferably contains the repeating- unit represented by the formula (1) an<d the repeating" unit represented by the formula (2-1) in an amount of 30% orr more, respectively. The repeating unit represented by the formula (1) and the repeating unit represented toy the formula (2 — 1) may contain only one kind, respectively, ox may contain two kinds or moxe, respectively. (Exemplified compound of type AA)

It is preferable that the copolymer of type α is a copolymer (type AA) containing the repeating unit represented by the formula (1) wherein at least one of R 1
and R 2
is an alkyl group having from 2 to 6 carbon atoms and a fluorine atom, or an aryl group containing a fluorine atom, and the repeating unit represented by the formula (2-1) . An alkyl group having 6 or

less carbon atoms is more preferable from the standpoint of synttiesis suitability .

In the case of t lie type AA, it i s- preferable tha ~
t R 1
and R 2
in the formula (1) each independently are an alkyl group having from 2 to 6 carbon atoms and a fluorine atom.

The alkyl group having from 2 "to 6 carbon atonLS and a fluorine atom may be any of linear, branched or cyclL c alkyl group. Further, the alkyl group having from 2 to 6 carbon atoms and a fluorine atom is preferably an alkyl group containing a fluorine atom, having from 2 to 4 carbon atoms, and is most preferably 2 , 2 , 2-trif luoroethyl group,

When R 1
and R 2
each are an alkyl group containing a ff luorine atom, having 7 or less carbon atoms, the polymer is difficult to have crystallizabifJLity, and transparency tends to improve, whiclh is preferable.

On the other hand, the aryl group containing a ff luorine atom preferably has from 6 to 9 carbon atoms. Aphenylene group is preferable, and a pentaf luorophenyl group i s more preferable.

When R 1
and R 2
are an alkyl group or an aryl group, not corresponding to the alkyl group having from 2 to 6 carbon atoms and a. fluorine atom and the aryl groiαp containing a ff luorine atom, those are preferably an alkyl group having from 1 to 9 carbon atoms (it may be any of linear, branched or cyclic alkyl group, and specifically, a methyl group, an ethyl grroup, an isopropyl group, a t-butyl group, a benzyl group, a cyclohexyl group, and the like are exemplified) or an aryl group having from.6 to 9 carbon atoms (specifically, a phenyl group, a p-tolyl group and the like are exemplified), and particularly preferably an alkyl grroup having from 1 to 4 carbon atoms.

In the ratio of the total hydrogen atom γL umber and fluorine atom number, contained in R 1
and R 2
, it is preferable that the fluorine atom number is hal f or- more the hydirogen atom number, and it is more preferable that the fluorine atom number is larger than the hydrogen atom n_ umber.

Preferable scope of the formula (2-1) is the same as in type A.

Further, preferable content rratio of the repeating unit represented by trie formula (1) and the repeating unit represented by the formula (2-1) Is the same as in type A. (Copolymer of type B)

A preferable second embodiment of the copolymer of the invention is a copolymer (type B) containing the repeating unit represented by trie formula (1) and the repeating unit represented by the formula (2-2) .

In the formula (1), when R 1
and R 2
are an alk:yl group, the alkyl group may be any of linear- , branched or cyclic form. The alkyl group has preferably from 1 to 10, and more preferably f J-TOm 1 to 6, carbon atoms. Specifically, preferable examples of the alkyl group include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a benzyl group, and a cyclohexyl group.

In the formula (1) , when R 1
and R 2
are an aryl group, an aryl group having from 6 to 8 caarbon atoms is preferable. Specifically, preferable examples of the aryl group include a phenyl group and a p-tolyl group.

At least one of R 1
and R 2
cont ains at least one fluorine atom. R 1
and/or R 2
, containing a fliαorine atom are preferably an alkyl group having from 2 to -6 carbon atoms and a fluorine atom (for example, 2,2, 2 — trif luoroethyl group,

In the formula (2-2), when R 5
and -R 6
are an allkyl group, the alkyl group may be any of linear, branched or cyclic form. The alkyl group has preferably from 1 to 10, and more preferably from 1 to 6, carbon atoms. Specifically, preferable examples of the alkyl groujp include a methyl group, an ethyl group, an lsopropyl group, a tert-butyl group, a benzyl group, and a cyclohexyl group. A methyl group J-S particularly pnref erable . R 5
and R 6
may be substituted with substitutents as described hereinafter. As the substituent that the alkyl group has, a halogen atom is particularly preferable.

In the forπrula (2-2), when R. 5
and R 6
are an aaryl group, the aryl group h.as preferably from 6 to 8 carbon atoms. Specifically, preferable examples of the aryl group include a phenyl group and a p-tolyl group.

The copolymer of type B off the invention preferably further contains the repeating unit represented by t2ie formula

(2-1), in addition to the repeating unit represented by the formula (1) and trie repeating unit represented by tine formula

(2-2) . The preferable scope and the like of R 3
and R 4
in the formula (2-1) are the same definition as described in the copolymer of type A.

The copolymer of type B off the invention preferably contains 20 mol% or more of the repeating unit represented by "the formula (1), and from 0.05 to 2 O mol% of the repeating unit represented by trie formula (2-2) .

In the case of further containing of the repeating unit represented by the formula (2-1),- it is preferable to contains 20 mol% or more of "the repeating uni t represented by t lie formula (1) , from 0.05 to 20 mol% of the repeating unit represented by the formula (2-2) , and 20 mol% or more of the repeating unit represented by the formula (2-1 ) . The copolymer of the invention may be that the sum of tlhose repeating units is 100

mol%, but may contain structural- units other than those.

In particular, when the repeating unit represented by the formula (2-2) is 20 mol% or less, decrease in transparency of a resin due to priase separation can effectively be suppressed, and when it is 0.05 mol or more, further sufficient mar resistance and antifouling property can be obtained when an antireflective film is formed.

It is more preferable to contain 30 mol% or nxore of the repeating unit represented by trie formula (1) .

It is more preferable to contain from 0.5 to 15 mol% of the repeating unit represented by the formula (2-2) .

In addition, it is more preferable to contain 30 mol% or more of the repeating unit represented by the forπrula (2-1) .

The copolymer of the invention contains at least the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2-2), but those may be contained in one kind alone, or in two kinds or more, respectively. Further, in the case of containing the repeating unit represented by the formula. (2-1), the repeating unit represented by "the formula (2-1) may be contained in one kind alone, or in two kinds or more.

Specific examples of the copolymer of the invention are exemplified below, but the invention is not limited to those specific examples, x, y and z each represent the proportion of the repeating unit (mol%), and. are 0<x+y+z<100 ("where z is not present, O<x+y<100) . Preferably, the proporrtions are l<x<99, and l<y<99, and it is preferable that x and y each are 30 or more. Further, repeating umits other than tkose may be contained.

The compounds of the following specific examples may be that chains are connected with each other by a crosslinking agent or a crosslinkable monomer:.

(SU-0501) and (SU-1001) show siloxane units originated from initiators VPS-0501 and VSP-1001 described hereinafter.

Exemplified compounds of type A

Exemplified compounds of type B

3O

The copolymer °f the invention is a transparent (ultraviolet to near infrared region) and amorphous copolymer, and is soluble in a general solvent (particularly/, tetrahydrofuran (THF) , ethyl acetate and acetone) .

The copolymer of the invention has a number average molecular weight (Mn) of preferably from 1,000 to 1,000,00O, more preferably from 2,000 to 800,000, and furrther preferably from 10, 000 to 60O, 000, particularly preferably from 50,000 to 400,000, and most preferably from 100, 000 to 3O0, 000, in terms off styrene conversion measured with a gel permeation ch_romatography.

The copolymer of the invention has a weight average molecular weight (Mw) of preferably from 2, 0OO to 1,000,00O, more preferably from 20,000 to 1,000,000, further preferably from 100,000 to 600,000, and particularly preferably from 150,000 to 600, 0O0.

The copolymer of the invention has Mw/KEn of preferably 3.5 or less, more preferably 2.5 or less, and furrther preferably 2. 0 or less .

The copolymer of the indention has a glass transition temperature (Tg) of preferably from 25 to 25O 0
C, more preferably from 60 to 200 0
C, further preferably from 80 to 18O 0
C, particularly preferably from 8O to 160°C, and most preferably from 80 to 13O 0
C.

The copolymer of the invention has an elastic modulus of preferably 800 MPa or more, and more preferably from 1,000 to 3, 000 MPa.

The copolymer of the invention has a tensile strength of preferably 20 MPa. or more, and more preferabLy from 25 to 45 MPa.

The copolymer of the invention has a ref rractive index of preferably 1.5 ojtr less, and more preferably IL.45 or less.

The copolymer of the JLnvention preferably has low hygroscopic property, and, for example, it is preferable that

a satmrated water absorption at 25°C is less than 1%.

The copolymer of the invention preferabILy has transparency.

Where the copolymer used in th.e invention obtained as above is used in, for example, optical materials such as optical waveguides as described hereinafter, it is preferable that the copolymer is a transparent (ultraviolet to near infrared region) and amorphous copolymer, and is soluble in a general solvent (particularly, tetrahydrofuiran (THF) , ethyl acetate and trie like) . (Polymerizable composition)

The polymer is obtained by polymerizing a polymeαrizable composition containing a compound represented by the formula (3), and at least one of a compound represented by the .formula (4) and a polysiloxane-containing compound. Formula (3) R 1
O 2
C-CH=CH-CO 2
R 2

In the formula (3) , R 1
and R 2
represent an alkyl group (excluding the case that the alk;yl group contains a group represented by ~~ (CX 2
) n
~X (X is a halogen atom, and n is an integer of 7 or more) ) , or an aryl group, provided that at leas ~
fc one of R 1
and R 2
contains a fluorine atom.

In the formula (3) , R 1
and R 2
are the same as defined in the formula (1) , and "the preferable s cope is also the same as defined therein. The unsaturated compound includes a trans form (fumaric acid die ster) and a cis form (maleic acid diester) , and may be either of those. Trans form is preferable.

Where R 1
and R 2
are the same (R 1
=R 2
=R) , the fumaric acid diester that is the compound represented by the formula (3) can be synthesized by a single step from commercially available fumaroyl chloride and alcohol as shown below. Where R" 1
and R 2
differ:, the compound Is obtained by using maleic anhydride as a starrting material, and successively /
reacting the same with two k-Lnds of the corresponding alcoho Is using, for example, a

method described in JP-A-8-160365.

Formula (4)

In the formula (4) , R represents an all-cyl group, an aryl group, an alkioxy group or an amino group (which may be an anilino group) , and R 4
represents an alkyl group.

In the formula (4 ) , R 3
represents an alkyl groujp, an aryl group, an alkoxy group or an amino group, and R 4
represents an alkyl group. R 3
and R 4
are the same as defined in R 3
and R 4
in the formula (2-1) , respectively, and the preferable scope is also the same as defined therein.

The compound represented by the fformula (3) , the compound represented by the formula (-4) and the ;polysiloxane-containing compound may be contained in two kinds or more, respectively. Further, other monomers may be contained. As sixch other monomers, monomers copolymerizable with the compound represented by the formula (3) , the compound represented by the formula (4) and/or the polysiloxane- containing comjpound can widely be used. Specific examples of the other monomex include

Trie preferable embodiment of the polyrnerizable composition of the invention is a poILymerizable composition containing, at least, a ~
t least one of the compound represented by the formula (3) and at least one of the compound represented by the formula (4) . Tbie ratio (molar- ratio) of the compound represented by the formxαla (3) and the compound represented by the formula (4) is preferably from. 60:40 to 40: 60. The preferable scope of the compound represented by the formula (3) and the compound represented by the formula (4) is the same as defined above.

Another preferable embodiment of the polyrnerizable composition of the invention is a poILymerizable composition containing the compound represented toy the formula (3) , the compound represented by the formul_a (4) and a siloxane unit-containing compound . Those compounds each, may be contained in only one kind or two kinds or more.

Specific examples of the compound represented by the formula (3) used in the invention are exemplified below, but the invention is not limited to those specific examples.

Specific examples of the compound represented by the formula (4) used in the invention are exemplified below, but the invention is not limited to those specific examples.

As the siloxane unit-containin g compound^ the exemplified compounds of the compounds .represented Hoy the formula ( 6 ) to ( 10 ) desc_ribed hereinafter? can preferably be employed -

It is preferable th at the copolymer of the invention is obtained by radical polymerization of the polymer- izable composition in the presence of a polymerizat ion initiatorr . The radical polymerization i s advantageous in the standpo int of easiness of operation because of allowing the pres ence of moisture ,. and has the merit that it is easy to obtain a rela tively high mole cular weight material . As the method of producing by radical polymerization, the conventional methods can b>e used for the production . Examples of the method that can b> e used include a. bulk polymerization, a solution polymerizat-Lon, an

emulsion polymerization, in water or in an emulsion, and a suspension polymerization. The polymerization method is appropriately selected depending on the performances required in optical members used. For example, in the case of a. core material of optical fibers, a bulk polymerization is pref e rable, and in the case of a cladding material of optical fiber" s, it is preferable to appropriately select from a bulk polymerization, a solution polymerization, an emulsion polymerization and a suspension polymerization.

A solvent used in the liquid polymerization is not particularly limited, but ethyl acetate, butyl acetate, in.eth.yl ethyl ketone or the like is preferably used.

di-tert-butyl-2, 2' -azobis (2-methylpr opionate) . Those polymer ±zation initiators may be used as mixtures of two or more thereof .

In the case of a process conducting in an aqueous medium, an organic free radical initiator such as a persulf ates or a "redox" compound can further be used.

A. chain transfer agent may appropriately be used for regulat ing a molecular weight. The chain transfer agent is used to regiαlate a molecular weight of the polymer. Thie chain transfer agent can appropriately select its kind and addition amount according to the kind of the polymerizable monomer. Chain transfer constant of a chain transfer agent to each monomer" can refer to, for example, Polymer Handbook, 3 rd"
Edition

(J. BRANDRUP and E. H. ZMMERGUT, Published by JHON WILEY & SON) . The chain transfer constant can further be determined by the experiment by reference to Takayukd. Ohtsu and Masayoshi Kinoshd-ta, Experimental Method of Polymer Synthesis, Kagaku— dojin Publishing Co. (1972) .

(such a.s thiophenol, m-bromothiopherxol, p-bromothiophenol, m-toluenethiol, and p-toluenethiol) , and the lzLke are preferably used. Of those, the alkyl mercaptans such as n-octyl mercaptan, n-lauryl mercaptan and tert-dodecyl mercaptan are more preferably used. Chain transfer agent in which a hydrogen atom in. C-H bond is substituted with a. heavy hydrogen, atom or a fluorine atom can also be used. The chain transfer a. gent may be used as mixtures of two or more thereof.

Polymerization temperature generally depends on decomposition rate of the polymerization initiator selected, and is preferably from 0 to 200°C, and more preferably from 40 to 120 0
C. Where a gaseous monomer is used as the cornonomer, polymerization is preferably conducted in a pressure vessel

such as an autoclave, and a pressure applied a-fc that time i s, for example, from atmo spheric pressure to 50 bar f
and pref erab Iy from 2 -to 20 bar.

Trie method of producing the copolymer of type A of t lie invention includes a method of obtaining a polymer Iby polymerizing the compound represented by the fformula (3) and the compound represented by the fformula (4), a.s shown belo"w. Other methods can also be used. The other methods include a method of polymerizing maleic anhydride and the compound represented by the formula (4), and esterifying by a polyirLer reaction, as shown in the follow ring reaction formula.

In the reaction, formula, R 1
"to R 4
are the same as defirred in R 1
to R 4
the formula (1) or (2-1) .

Introduction sd_te of the repeating unit (siloxane unit) contained in the copolymer of type B of the invention and introduction method thereof are not particular ILy limited, b»ut the following three methods axe the representative a.nd preferable method.

(1) A method of introducing a fumarate having s siloxane un.it as one of monomers into a side cϊiain.

(2) A method of introducing into a side chain using a virxyl monomer- having a siloxane unit.

(3) A method of introducing into a side chain us J_ng an initiator having a siloxane und-t.

(1) A method of introducing a fumarate having a siloxane unit as one of monomers into a main chain.

It is preferable to use a compound represented by the following formula (6) (fumaric acid ester or maleic.: acid ester) as one of raw material s . Formula (6)

In the formula (6), at least one of R 7
and R 8
is a substituent represented by the following SU-I:

In the above formula, R 9
to R 13
each represent a hydrogen atom, an alkyl_ group or an aryl. group, L 1
represents a connecting group having from 1 to 20 canrbon atoms, n is an integer r of 0 or 1, and p is an integer of from 10 to 1O00. When only one of R 7
and R 8
i s SU-I, the other represents an alkyl group or an aryl_ group.

When R 7
and R 8
arre an alkyl group, the alkyl group may be any of linear, branched and cycli_c form. The alkyl group has preferably 10 or less, and more preferably 5 or less, carborx atoms. Specific examples of the alkyl group incJLude a methy]_ group, an ethyl group, γL— propyl group, isopropyl grroup, n-butyl_ group, tert-butyl group, tzrrif luoromethyl group,

2-triflταoroethyl group , and IH, IH, 3H— tetraf luorojpropyl group.

Wlien R 7
and R 8
are an aryl group, the aryl group preferably has from 6 to 8 carbon atoms . Preferable examples of the aryIL group include a phenyl group, a methylphenv'l group, a. pentaf liαorophenyl groixp, and p-methoxyphenyl group.

Wlien R 9
to R 13
are an alkyl group, the alkyl group may bes

any of linear, branched and cyclic form.. The alkyl group has preferably 10 or less, and more preferably 5 or less, carbon atoms . Specific examples of the alkyl <group include a methyl group , an ethyl group, n— propyl group, isopropyl group, n-butyl group , tert-butyl group, triff luoromethyl group,

2-trl f luoroethyl group, and IH, IH, 3H-tetraf luoroprop^/1 group.

When R 9
to R 13
are a_n aryl group, the aryl group prreferably has from 6 to 8 carbon atoms. Preferab_Le examples of the aryl group include a phenyl group, a methylphenyl cgroup, a pent a fluorophenyl group, and p-methoxyphenyl group.

As R 9
to R 13
, an aXkyl group is preferable, and a methyl group is particularly preferable.

L 1
is preferably an alkylene group having 5 or less carbon atoms . p is preferably an integer of frrom 30 to 500.

R 7
to R 13
may have a substituent. As the substituent, in addition to a halogen atom (preferably a fluorine atom), substituents exemplified as the substi tuents of the above R 1
to R 6
are exemplified a_s the preferable examples.

Specific examples of the compound represente d by the formula (6) are exemplified below, but the invention is not limited to those specific examples.

(2) A method of introducing into a side chain using a_ vinyl monomer having a siloxane unit

It is possible to use as a raw material an optional siloxane-containing vinyl monomer cojpolymerizable wiirh the compound represented by the formula (4) and the compound ^represented by the formula (5) . For example, it is prefferable "to use at least one of a compound represented by the following formula (7), a compound represented by the following fformula

(8) and a compound represented by the following formuJLa (9) .

In the formulae (7) to ( 9) , R 14
represents a hydrogen, atom, a methyl group or a trif luoromethyl group, and a hydroge:n atom and a methyl group are preferable.

The def-Lnition and preferable examples of R 9
to R 113
, L 1
, p, n in SU-I are the same as defined in tlhe formula (6) , and the preferable scope is also the same as defined therein.

Specific; examples of "the compounds represented toy the formulae (7) to (9) are exemplified below, but the invention is not limited to those specific examples.

(3) Amethod of introducing into a main chain using an_ initiator having a. siloxane unit

By using an initiator having a. siloxane urxit in the molecule, it is possible to introduce the siloxane unit into the main chain. The kind of the init iator having a. siloxane unit is not parti- cularly limited, but a siloxane unit-containing azo initiator having a repeating unit represented by the following formula (HO) is exemplified as the example _ Formula (10)

In the formula (10), R to R each represent an aHkyl group or an arryl group, and x is an intege_r of from 10 to 1,000.

When R 15
to R 18
in the formula ( 10) are an allkyl group, the alky^l group maybe any of linear, b xanched and cyclic form. A linear: or braqnched alkyl group is preferable. The alkyl group has preferably IO or less, and more preferably 5 or less, carbon atoms. Specific examples of ttie alkyl group include a methyl cjroup, an ethyl group, n-propyl group, isopropyl group, n-butyl group, tert- butyl group, trif luorometh^/l group, 2-trif ltαoroethyl group, and IH, lH-pentaf luoroprop^l group.

When R 15
to R 18
in the formula (1O) are an aryl qroup, the aryl group preferably has from 6 to 8 carbon atoms. .Preferable examples of the aryl group include a phenyl group, a methylphenyl group, a pentafluorophenyl group, and p-metho>cyphenyl group _

X preferably is an integer of rfrom 30 to 500.

Specific exampl_es of the si_loxane unit-containing initiator represented by the formula (ILO) are exemplified below, but the invention is rxot limited to those specific examples.

Of those, VPSlOOl (10-1) and VPS0501 (10 — 2) that are the polysiloxane-coritaining azo Initiators, products of Wako IPure Chemical Industries, Ltd., are exemplified as the particularly preferable example .

When polymerization is conducted using those siloxane unit-containing initiators , other general radzLcal polymerization initiators may be used together.

Other than the raw material monomers of the copolymer of the invention ( for example, the compound represented by the formula (3), the compound represented by the fformula (4) , and the compound represented by the formula (6)), optional vJLnyl monomers (monoiaer C) copolymerizable with the raw material monomers may be used. The monomer C can has a function, of imparting adhesion or solvent solubility, or as a crosslink≡ible group or a substzituent for connecting crosslinkable grouαps .

Specific examples of the radical polyme xizable monomer C are exemplified below, but trie compounds thai: can be used in the invention axe not limited to those specific examples.

Polymerization reaction for obtaining "
the copolymer of the invention is preferably tihat a reaction solution obtained by the polymerization reaction can directly b>e used as a curing resin composition, and it is preferable to conduct the rea ction in a solution polymerization system using an. organic solvent. Examples of the preferable po IL ymerization solvent include (1) esters such as ethyl acetate, butyl acetate, i_ sopropyl ace tate, isobutyl acetate and cellosoILve acetate; (2 ) ketones sixch as acetone, methyl ethyl ketone, methyl isotoutyl ketone and cyclohexane; (4) cyclic ethers such as tetrahydrofuraπn and dioxane; (4) amides such as N, N-dimethyL formaldehyde and N, N-dimefc hylacetoamide; and C 5) aromatic hydrocarbons such as toluene and xylene. Of those, esters, ketones and etherrs are preferable. Ethyl acetate, acetone and metϊiyl ethyl ketone, that do not have a high boiling point, and do not have load in drying, a jce particularly preferable . If necessary, alcohols, aliphatic; hydrocarbons and the like can be used and mixed.

The copolymer of the invention may" be obtained by appropriately subjecting the reaction solution obtained by polymerization reaction to a post-treatment . As the post-treatment , a general jreprecipitation. treatment (for example, a purification metliod of adding a polymerization reaction solution to an insoILubilizing agerxt of a copolymer, comprisirxg an alcohol, or "the like, and insolubiliz ation precipitating the copolymer) can be conducted , and subsequently, by dissolving the solid copolymer obtained in a solvent, a specific copolymer solution can be prepared. Further , the polymerization reaction solution from which residual iαon_omers have been removed can directly be used as a specific copolymer solution.

Practically, the curing resin composition off the invention, preferably has curing properties. Where the copolymer: itself does not have sufficient curing properrties, necessary curing properties may be imparted, or curing

characteristics may be improved, by further adding- various crosslinkable compounds, additives, polymerization initiators and the like, thereby forming a three-dimensional crosslinking structure or IPN (Inter Penetrating Network) structure. Where the crosslinkable compound is used,- a mixture of the crosslinkable compound and the copolymer can be used as the curing resin composition, or a reaction product obtained by reacting the whole of the specific copolymer and crosslinkable compound, or a reaction product in a state that only a part of those has been reacted, can be used as the curJLng resin composition.

The curing resin composition used in the invention is preferably in a form, of liquid, contains the copolymer of the invention and a solvent dissolving thxe same, as essential constituents, and ±s prepared by dissolving various crosslinking agents, additives and polymerization initiators according to need. In this case, concentration of the solid content is appropriately selected accorcding to the use, but is preferably from 0.01 to 60 mass%, more preferably from 0.5 to 50 mass%, and further preferably from 1 to 20 mass%.

The solvent contained in the curing resin composition is not psarticularly limited so long as the composition containing the copolymer of the invention is uniformly dissolved or dispersed without generating precipitates. The solvent may be used as mixtures of two or more thereof. Examples of the preferable solvent include ketones (sixch as acetone, methyl ethyl ketone and methyl isobutyl ketone) , esters (sucti as ethyl acetate andbutyl acetate) , ethers (such as tetrahydrofuran and 1, 4-dioxane) , alcohols (such as methanol, ethanol, zLsopropyl alcohol, butanol and ethylene glycol) , and aromatic hydrocarbons (such as toluene and xylene) . As described before, it is preferable trxat a reaction solution obt ained by polymerization reaction can directly be used as the curring resin composition. Therefore, it is preferable that the

polymerization catalyst further functions as t lie solvent contained the curing resin compositio n . It is more preferable that the reaction solution obtained by the polymerization react ion is further di luted with a suitable amount of the same kind of a solvent as tϊie polymerization solvent, and is used.

If necessary, additives such as fine particle s of silica or the like , various si lane-coupling a gents or their hydrolysis partial condensates , surfactants , thickening a.gents and level ing agents may appropriately be added to the curing resin compo sition .

Curing manners of the copolymer contained in the curing resin composition of tune invention include the following three methods .

A first method is a manner of imp arting a funct ±onal group such as a hydroxyl group or an amino group to a siede chain of a copolymer, and reacting with a pol ;yf unctional crosslinking agent such as a p olyf unctional isocyanate to form a three-dimensional cro sslinking structure , a second method is a manner of imparting a polymeri zable group such as a (metn ) acryloyl group to a side chain of a copo lymer, and react ing with a polymerization initiator t o form a three-dimensional cro sslinking structure, and a third method is a manner of adding a compound having a monofumcional or polyffunctional polymerizable groups to a copolymer, and polymerizing in a mixed state to cause interlocking of polymers with each other, although no direct bonding therebetveen . Thus , curing characteristic s are improved -

Those curing manners are speci f ically described below. ( 1) The first manner is a curing res iLn composition, comprising a combination of a polyfunctional crosslinking agent and a copolymer having a functional group ^-reacting therewith . When the copolymer of the Invention has a hydroxyl groαp at a side chain, the hydroxyl. group at a side chain and the (polyfunctional ) curing agent are reacted to cure . A method

of introducing a hydrox;yl group into the copolymer of the invention j_ s preferably a method of introducing a hydroxyl group or a copolymer having a protected hydiroxyl group into a side chain as one of copolymenrizable components, and if necessary deprotecting.

On tune other hand,, the (polyf unctional) cros slinking agent used may be an oligomer or a pol^ymer. Depending on the kind of the (polyf unctional) curing agent used, the curing manner can be classified into (I) a curing using an amino resin,

(II) curing using a polyfαnctional isocyanate, and (III) curing using a cat-ionic polymerizable crosslin. king agent . In- the case of conducting curing by an amino resin, as in (I), examples of the amino uresin used incILude a urea resin, a melamine resin, a benzoguanamine resin and an acetoguanamine resin. The melamine resin is particularly preferable from the points of performances of a cured film and costs. In the case of conducting curing using a polyfunctions 1 isocyanate as in (II) , examples of the polyfunctional isocyanate used include triphenylmethane triisocyanate, toluylene diiso cyanate, xylene dϋsocyanate and hexamethylene diiso cyanate . Toluylene diisocynate is particularly p referable from the point of reactivity. In the case of conducting curing by a cationic polym.eriza.ble crosslinking agent as in (III) , the cros slinking agent used preferably has a ring opening polymerizable group such as an epoxy group, an oxetanyl group* and an oxazoline group, as a cationic polymerizable group. The crosslinking agent having an epoxy group is particularly preferable _ Those crosslinking methods (I) , (II) and (IZI) may be used alone or as combinaiiions of two or three methods. The cross linkable compound used in (I), (IEI) and (III) is not limited to the compounds shown herein, and crosslinkíLng agents shown in, for example, Handbook of Crosslin '
king Agent, Taiseisha , may be used.

(2) The second method is a manner of imparting a polynnerizable

group sυch as a (meth) acryloyl group to a side chain of a copolymer, and reacting with a polymerization initiator to form a three — dimensional cirosslinking structure. Un the case thtat the strructure of trie copolymer is a f luo xine-containing copolymer having a (meth) acryloyl- group introdiαced into a side chain, curing is conducted by radical polymerization of the

(meth) acryloyl group introduced. As the method of introducing the (meth) acryloyl group into the copolymer, time following (a) to (f) methods are preferable. That is, the methods are Qa) a method of synthesizing a copolymer having a nuoleophilic group such as a hydroxyl group or a.n amino groiαp, and acting

(meth) acrylic acid ch-loride, (me ~
th) acrylic acid anhydride or a mixed acid anhxydride of (meth) acrylic acid and methane sulfonic acid, (b) a method of acting (meth) acrylic acid to the copolymer having a nucleo^philic group in the presence of a catalyst such as sulfuric acid, (c) a method of acting a compound having both an isocyanate group and a. (meth) acryloyl group, such as methacryloyloxypropyl isocyanate, to the copolymer having a nucleophilic group, (&) a method of synthes izing a copolymer having an epoxy group, and acting

(meth) a crylic acid, (e) a method of acting a compound having both an epoxy group and a (meth) acitryloyl group, such as glycidyl methacr ylate, to a copolymer having a carboxyl group, and Cf) a methiod of polymerizing a vinyl monomer having a 3-chlor opropionic acid este.tr site, and conducting dehydro chlorination. Of those, (a) or (b) is preferable to particularly a copolymer having a hydroxyl g ~
roup.

T lie radical poiymerizatiorx initiator can use either of an initiator generating radicals Iby the action of heat (thermal polymerr ization initiator) and an initiator generating radicals by the action of light (photopolymerization initiator) .

(3) Trie third method is a matine r of adding a compound having a monof uncional/polyfunctional polymerizable group to a copolyirt-er, and polymerizing in a mixed state to cause

interlocking of polymerrs with each other, although no direct bonding "therebetween. The copolymer itself of tlhe invention does not require introduction of a functional group as in (1) or (2) . The copolymer: is cured by adding a polymerizable compound having an ethylenically unsat iirated group thereto, and irradiating with an active energy in the presence of a photopol ymerization ini_tiator or heating in the presence of a thermal polymerization initiator. Th.e polymeriza.ble compound used has preferably 2 o_r more, and more preferably 5 or more, ethyleni cally unsaturated groups in one molecule. Examples of the monomer having 2 or more ethylenioally unsaturated groups include esters of a polyhydric alcoho 1 and (meth) acrylic acid (for example, ethylene glycol di (meth) acrylate,

In the above (2) or (3) , when a compound initiating radical polymerization by the action of heat is "
used, curing of a f-Llm is conducted by heating. As sucti a thermal polymerization initiator, organic or inorganic peroxides, organoazo or diazo compounds, and the like can be used. Specifically, examples of the organic peroxide include benzoyl peroxide (BPO), tert— butylperoxy-2 —ethyl hexa.nate (PBO) ,

4, 4-azobis (4-cyanopentanoic acid) . The polymerization initiator may be used in two kinds or- more.

When -the curing is conducted by heat, the curing tempejrature is preferably from 30 to 200 0
C, more prefer- ably from 80 to 180 0
C, and particularly preferably from 100 to 150 0
C. The heating time is preferably from 1 second to 100 hours, more preferably from 5 seconds to 20 hours, and particularly preferably from 10 seconds to 1 hour.

A photosensiti-zer may be used in addi_tion to the phot opolymerization initiator. Examples of the phot osensitizer include n-buty^lamine, tirriethylamine , tri — n-butylphosphine , Michler' s ketone and thioxanthone.

When curing is conducted by light, irradiation wit Ih active energy rays is preferably conducted using a high pressur e mercury lamp or 365 mm LED. In this case, ultraviolet: irradiation is conducted under the condition of oxygen concentration of preff erably 0.5% or Hess, more prref erably 0.3% or less, and particularly preferably 0.2% or less. Irradiation energy is in a range of preferably from 300 to 1,500 mJ/cm 2
, more preferably from 400 to 1,000 mJ/cm 2
, and particularly preferably from 500 to 800 mJ/cm 2
.

The addition amount of the compound initiating radical polymerization by the action of heat or light is a.n amount that can initiate polymerization of carbon-carbon double bonds. In general, the amount is preferably from 0.1 to 1.5 mass%, more preferably from 0.5 to 10 mass%, and particularly preferably from 2 to 5 mass%, to the total solid contents in the curing resin composition.

The cured film made from the curing resin composition o f the invention forms a low refractive index layerr and also ha s

mar resistance, and therefore can be ext ended to various optical material uses. For example, it can advantageously toe used in formation of optical materials such as .an antiref leotive film and optical fiber clad. Further, uizilizing high fluorine content, it can suitably be used as materials for paint to a substrate requiring weatherability, materials for weatherable film, coating materials, and the like. Of those, use as an antiref lective film is particularly useful, and when the film is applied to various displays, its visibility can be improved.

Application to an antiref lective film havi_ng a low refractive index laye_r comprising the curing resin composition having" the copolymer of the invention (sometimes referred to "low reflective laminate") is described in detail below. In particular, the copolymer of type B can. preferably be employed to those uses. Layer structure of antiref lective film

The antiref lect ive film of the invention can have various layer structures, but has a layer structure comprising a transparent substrate, if necessary, a hard coat described hereinafter on the substrate, layers laminated thereon considering refractive index, film thickness, number of layers, order of layers, and "the like, so as to decrease ref lectivity by optical interference. The simplest structure of the low reflective laminate d_ s a structure comprising a substrate and only a low refractive index layer formed thereon. To decrease the reflectivity, it is preferable that the antiref lective layer is constituted toy combining a higlh refractive index layer having a refractive index higher than that of the substrate and a low .
refractive index layer having a refractive index lower than that of the substrate.

Examples of the preferable layer structure of the antiref lective film of the invention are shown below. In the following structures, the substrate film functions as a support.

The layer structure is not particularly limited to those structures only so long as reflectivity can be decreased by optical interference.

The antistatic layer is preferably a layer containing conductive copolymer particles or metal oxide fine particles (for example, ATO and ITO) , and can be formed by coating, atmospherric pressure plasma treatment or the like.

The above examples show a structural exampl_e of an antiref lective film that does not have glare-proof property, but can preferably be applied to glare-proof, antire f lective films. In this case, tine glare-proof property can be imparted to any off the above layers. High and middle refractive index layers

Materials for fo_rming high and middle refractive index layers and hard coat layer in the ant iref lective f il_m of the invention are described below.

The high and middle refractive index layers in the antireflective film of the invention has refractive index of preferably from 1.50 to 2.40, and more preferably from 1.50 to

1.80.

The high and middle refractive index layers , of the invention contain at least a. binder for forming a coating film, and can further contain an inorganic filler in order to i ncrease refractive index of the layers and redmce curing shrinkage.

As the compound generating an acidby the action of light, various examples are described in, for example, Imaging Organic Materials, p 187-198, Organic Electronics Material Society, Bun-Shin Shujppan, and JP-A- 10-282644, and those conventional compounds can be used. Specifically, examples of the compound include various onium salts such as a diazonium salt havi ng RSO 3
- (R represents an alkyl group or an aryl group) , AsF 5
-,, SbF 6
-, PF 6
-, BF 4
- orr the like as a counter ion,, an ammonium salt, a phosphonium salt, an iodonium salt, a sulfonium salt, a selenonium salt and an antrronium salt; orrganic halides such as oxadiazol derivatives in which a trihaILomethyl group has be substituted, and S-triazine derivatives; o-nitrobenzne esters of an organic acid; benzoin esters; inimo esters; and di_ sulf one compounds. Onium salts are preferable, and sulfonium salts and iodonium sal ~
bs are particularly preferable.

The antireflective film of the invention preferably has a middle refractive index l "
a.yer having a rrefractive index lower than that of the high refr: active index ILayer and highier than that of the support. The middle reflectiLve index layezc can be formed in the same manner as in the high rrefractive index layer by controlling the amount 0 ± a high refractive index f iILler and a high refractive index monomer, used in the high reffractive index layer.

The anti_ref lective film may further tiave a hard coa ~
t layer, a moisture-prroof layer, an antistatic layer, an undercoat layer or a protective layer . The riard coat layeir is provided to impart mar resistance to a transparent support- The hard coat layer has a function to strengthen adhesion between the support and a layer thereon. The hard coat layer can be formed uxsing an

acrylic copolymer, a urethane copolymer, an epoxy copolymer, a silicone copolymer, a silica compound or the like. A pigment may be added to the hard coat -Layer. The acr-ylic copolymer is preferably synthesized by polymerization. reaction of a polyf unctional acrylate monome x (for example, apolyol acrylate, a polyester acrylate, a urethane acrylate and an epoxy acrylate) . A melamine polyixrethane is included in th_e samples off the urethane copolymer. As the silicone copolymer , a cohydrolyzate of a silane compound ( for example , a tetralkoxysilane and an alkyl trialkoxysilane) and a silane coupling agent having a reactive group (for example, epoxy and methcarylic) is preferably used. Two or more of the copolymers can be used in combination. As the silica compound, colloidal silica is preferably used. The hard coat layer has strength off preferably H or more, more preferably 2H or more, and most pref erably 3H or more, in terms of a pencil hardness of 1 kg load. An adhesive layer, a shielding layer , a sliding layer or an antistatic layer may b e provided on_ the support, in addition to the hard coat layer. The shielding layer is provided to shield electromagnetic waves or infrared rays.

The antireflective film of the invention is preferably used as a protective layer of a polarizing plate.

On the othenr hand, the copolymer A (preff erably, copoLymer AA) is preferable as a material, of an optical member. Examples off the optical member containing the polymer of the invention include optical waveguides (particularly, optical fibers) , lenses for still camera, video camera, telescope, eyegl_ass, plastic contact Lens, sunlight collection or the like, mirrors such as concave mirrors or polygonal mirrors, and prisms such as pentaprisms. -A polymer having very small birefringence can be obtained by sel_ecting high heat resistance , high hygroscopic property and monomers. Therefore, it is possible to use the same in substrates such as a scattering plate or an optical disc, and an optical s ~
witch.

The embodiment that an optical fiber having a core portion and a clad portion, is prepared ±s described below. Using- a solution or a solid of the polyiner, an. optica, 1 fiber preform can be produced by, for example, "
the following methods ((1) is described in JP-A-11-109144 (page 7, Mode for Carrying Out the Invention)) . However, the method is not limited to those methods .

(1) A method of producing a pref orm by melting" a thermoplastic resin, pouring a melt of the pol_ymer of the invention in the central portion ttiereof, furthest: pouring a refractive incdex regulator or the polymer containing a refractive incdex regulator in the central portion thereof, and heat diffusing the refractive index regulator.

(2) A method of "
producing a preform by forming a tube comprising a hollow thermoplastic resin on the outermost la^/er utilizing a rotating glass tube OJC the like, poxαring a solution of the polymer of thte invention and a refractive index regulator ±n the hollow portion, evaporating an organic solvent to form a layer by reducing pressure or heating, whi]_e rotating, and simultaneously progressively increasing the amount of the refractive index regulator added.

( 3) In the production methods of (1) and ( 2) , a method of producing a prefonrm without containing a refractive index regulator.

( 4) A method of producing a hol_low preform by forming a tube comprising a hollow thermoplastic resin on the outermost layer utilizing a rotating glass tube or the 1 ±ke, pouring- a polymerizable composition (monomers, a polymerization initiator, a chain transfer agent, if necessary, and a refractive index regulator if necessary) capable of producing the polymer of the invention (The thermoplastic resin is a. polymer having a. different refractive index, and the refractive index is preferably higherr than the thermoplastic: resin. Uts refractive index is preferable 0.001 or higher, more preferably

0.005 or higher, and further pref errably 0.01 or hi <gher . ) in the hollow portion, and polymerizing by heat or licfht. (5) In (4), in producing a hol_low preform o_f a rotating polymer having plural layers iα a concentric fashion by polymerizing stepwise the polymer iLzable composit ion, a method of producing a pref orm by using a plural kinds of monomers having different refractive indexes, and progressively increasing their refractive indexes toward the center. In tHnis case, the outermost thermoplastic resin layer is not essential.

The thermopLastic resin used in the above methods can be any thermoplastic xesin so long as it imparts sufficiently high mechanical strength under use temperature of optical fibers. It is preferable to have tensile modulus at room temperature of 2,000 MPa or more. Of those, particularly representative examples include a polymethacryl ate resin, a polycarbonate resin, a linear polyester resin, a polyamide resin, an. acrylonitrile/styarene copolymer resin (AS resin) , an. acrylonitrile/butsdiene/styrene copolymer resin (ABS resin) , a polyacetal resin, a cyclic polyolefin resin, a. polystyrene resin, a tetraf luoroethylene copolymer resin and a chlorotrif luoroettiylene copolymer? resin.

The refractive index regulator is called ≡L dopant, and. is a compound having refractive index different from the refractive index of the polymer or polymerizable monomer used. The refractive index is preferably 0.005 or higher . The dopant- has the property to increase refractive index off a copolymer- containing the same as compared with a copolymer not containing- the same. As compared with the polymers formed by "the synthesis of monomers, as des cribed in Patent No. 3332922 or CTP-A-5-173026 , those are that difference in solubility parameter is within 7 (cal/cm 3
) 372
, and difference in refractive index is 0.001 or more, and have the property to increase refractive index of a copolymer containing the same as compared with a copolymer not- containing the same. Any compound that can stably be present

together with trie polymer, and is stable under polymerization conditions (polymerization conditions such, as heating" and pressurizing) of the polymer izable nxonomer as the above-described raw material can be used.

The dopant may be a pol_ymerizable compound. Wh_en a polymerizable compound is used as the dopant r
it is pref errable to use a compound, having the property that a polymer containing the same as a copolymerizing coπvjoonent increases its refractive index as compared with a polymer not contain. ing the same . In the invention, a refractive index distribution type core portion may be formed by selecting plural kinds of monomers having different refractive indexes, and progressively changing its compositional ratio. Further, compounds that have the above properties, can stably be present together with the polymer, and. is stable under polymerization conditions

(polymerization conditions suclα as heating and pressurizing) of the polymerizable monomer as the abo ~
ve-described raw material can also be used as the dopant . By f oarming a refractive index distribution type core portion using the dopant, an optical member obtained is a ref uractive index distribution, type plastic optical fiber having a wide transmission band.

Examples of the dopant include those disclosed in Japanese Patent No. 3332922 and JP-A-11-142S57 such as benzyl benzoate (BEN) , diphenyl sulfi_de (DPS) , truphenyl phosphate

perfluoroacetophenone, perf luorobiphs.en.yl, chlorohepta £ luoronaphthalene and bromheptaff luoron.aphtha.lene . Of those, BEN, DPS, TPP, DE 3
SO, diphenyl sulfide and its derivatives , dithiane derivatives and bromobenzene are preferably used in the optical waveguide of the invention. Specific example of diphenyl sulfide and its derivatives, and dithiane derivatives are shown below. However, the invention is not limited to those.

Compounds in which hydrogen atoms present in those dopant compounds have been substituted with heavy tiydrogen atoms can be used for: the purpose of improving transparency in a. wide transmission band. Further, polymerizable dopants sαch as tribromophenyl methacryalte can also be used. When the polymerizab Ie compound is used as the dopan ~
t, a polymerd_zable monomer and a polymerizable refractive index regul_ating component axe copolymerized in forming a matrix. Therefore, it is more difficult to control various characteristics (particularly, optical characteristics), but there i s the possibility to be advantageous in the point of heat resistance.

When the polymer of the invention is used in the core portion, a polymer having less C-H bonds is preferable, and a polymer i_n which C-H bonds are substituted with C-D bonds is preferabXe. By using the polymer j_n which C-H bonds are substituted with C-D bonds, transmission loss can further be decreased.

As the method of preparing the core porti on having Graded-Index (GI) type refractive inde;x distribution using the dopant arxd the polymer of the invention, the following methods

(I) and (II) are preferable. However, the invention, is not limited to those methods _

(I) A cylindrical molding a comprising a. f luorine-con-taining polymer and a columnar moILding b comprising the polymenr of the invention containing a dopant are prepared by melt extrusion molding. The molding b is inserted in the molding a. By heating, the dopant in the molding b is melt dispersed to form GI type xefractive index distribution. This method is one embodiment of the above method (1) .

(II) A solution of a fluorine-containing polymer is poured in a cylindrical molding, and. while rotating, pressure is reduced to remove a solvent, thereby a layer comprisL ng the fluorine — containing polymer is formed on an inner surface of the cylindrical molding. A solution of a polymer containing a dopant ±s then poured, aad while rotating, pressure is reduced to remove a solvent, thereby a layer comprising the copolymer containing '
a dopant is .formed on an inner surface of the fluorine — containing polymer layer. WThile increasing the amount o£ the dopant added, the same operation as ai>ove is repeated to form plural layers, thereby imparting GI type refractive index distribution. This method is one embodiment of the above method (2) .

(III) A polymerizable composition containing at least one compound represented by trie formula (3) , at least one compound represented by the f ormul a (4), other monomers if necessary, and a dopant is poured in a cylindrical vessel such as a glass tube, and while rotating, a solvent is removed to forma, layer. Using a polymerizable composition having di. f f erent concentration of a dopant , this operation is repeated to form plural 3_ayers having a dopant concentration successively increasing toward the center from the outermost layer, thereby producing a hollow preform. (PF)-. Alternatively, using at least two kinds of at least one of the compound represented by the formula (3) and the compound represented by the formula (4) ,

polymerizati on is conducte d while rotating to form a layer . Using a jpolymerizable composition having different compositiona l ratio of monomers , this operation is repeat ed to form plural .L ayers having a copolymerizati on ratio of a monomer having high r efractive indeed successively increasing towarrd the center from the outermost layer, thereby producing a hollow preform (PF) .

Additi onally, other additives can b e added in a raage of not decreasing optical transmission performance . For example, a stabilizer can be added for the purpose of improving weather resistance or durability . Further, a stimulated emi ssion function compound for light signal amplif ication can be added for the purpo se of improving/ optical transmission perf ormance . By adding the above compound, an attenuated signal ligh ~
t can be amplified by excited light , thereby transmission dis ~
tance is improved . Therefore , it can be used in , for example, a part of a light transmission link as a fiber amplifier . Thos e can be contained by polymerizing after addi ng the raw material monomers .

An opt ical fiber can be prepared by melt stretchin g the preform. St retching is preferably conducted such that the preform is passed through tune inside of a .heating furnace ( for example , a cylindrical heat ing furnace) orr the like to heat and melt the same , and is then continuously stretch-spun . The heating temperature can app ropriately be determined depending on the properties or the li ke of the prefo rm, but is geneirally preferably from 180 to 2 50 0
C . The st retching conditions ( stretching temperature and the like) c an appropriately be determined, considering a diameter of a preform obtained, a diameter of a. desired optical fiber, materials used, and the like . In particular, a refractive inde:x distribution type optical fibe x has a structure- such that the refractive i±ndex changes from, a central direction of its cross section toward the circumference thereof - Therefore , it is necessary to

uniformly h eat and stretch. —spin so as not to destroy this distribution . Consequently , it is preferable for heating the preform to use , for example , a cylindrical- heating furnac e that can uniforml y heat the perforrm in the cross -sectional direction . The heating furnace pref erab Iy has temperature distribut ±on in a stretching" axis direction . With narrowzLng the molten portion, the shape o f refractive index distribution is difficult to distort , and yield incxeases , which is preferable . Specifically, it is preferab le to conduct pre-heating an <d slow cooling before and after the molten region such that a iregion of the molten portion narrows . Further, a. heat source th at can supply high output energy eve n to a narrow rregion, such as laser , is more preferable as the hea t source used in the molten region .

As de scribed above, "there is the case that a hollow preform is obtained depending on the production method of the preform. Where such a hoi low preform is stretched, it is preferable to conduct the stretching under reduced pres sure .

The stretching is preferably conducted usi_ng a stretch-spinning apparatus Ihaving a self "
centering mechanism maintaining a center position constant in order to maintain a linear form and its roundness . By selecting the stretching conditions , orientation of the polymer of fiber can be controlled, and mechanica J. properties ( such as bending performance ) , heat shrinkag e and the likie of fibers obtained by drawing oan be controlled . Tension at drawing can be 10 g or more in order to orient a molten plastic as described in JP-A-7-234322 , or is preferably 100 g or less in order to not retain strain after melt stretching" as described in JP-A-7-234324 . Further, fozr example , a method of conducting a preheating step in stretctiing can be employed as described in JP-A-8-1 O 6015 . Fibers obtained by tine above methods can improve bending or lateral p ressure characteristics of ffibers by prescribing elongation a ~
t break or ha. rdness of an element wire obtained as described, in JP-A-7-2. 44220 . Furth&r, as

described in JP-A-8 -5452 IL , a low refractive index l_ayer is provided! on the outer circumference to function as a refflective layer, thereby transmis sion performance can further be improved .

It is preferable that transmission loss of the optical fiber off the invention is , for example , 150 dB/km at drying .

Further, it is pre ±erable that l_oss increase at wet heating of the optical fib er of the inven tion is , for example ,

15 dB/km or less under the conditions of 75°C and 80% humidity .

Trie optical fiber produced by the above methods can be applied to various uses as it is . Further , the optical fiber can also be applied to various uses in an embodiment having a covering layer on the outs ide , an embodiment of having a fiber layer, and/or a state of bumdling plural .fibers . The covering step, for example , compr ises pas sing a. fiber eleme nt wire through facing dies having holes passing through thxe fiber element -wire , filling a covering molten resin between t_he dies , and movi_ng the fiber element wire betwe en the dies , thereby obtaining a covered fiber . It is desirable that the covering layer do es not weld with the fiber element wire in order to protect from, stress to the inner fiber when bending . Further, in this case , because thermal damage is added to thte fiber element wire when contacting with a molten resin,- it is desirabl_ e to select a resin that can be meILted at a moving speed suppress ing the damage as possible , or low temperature . In this case, thiickness of the covering layer depends on a melting temperature of a covering material , a drawing spee d of an element wire and a coolincj temperature oif the covering, layer . Besides , a method of polyme xizing. monomers applied to an optical member, a method of winding a sheet , a method of inseicrting an optical member in a hollow tube extrusion molded, and the like are known .

An. optical fiber cable can be produced by coverring the element wire . In such a ca se , the coverin g embodiment iLncludes

an adhesion type covering in which, the optical _f iber eleme nt wire is contacted and covered with the covering material ov er the entire circumference at the interface, and a loose type covering in which spaces are pre sent between the coveri ng material and the optical fiber element wire . In the loose type covering, for example , when the covering layer is peeled in connecting portion with a connecto r , there is th e possibili ty that moisture permeates from the space at the edge , and dif fus es in a longitudinal d irection . Therefore , the adrxesion type is generally preferable . However, in the case of t he loose type covering, because trie cover and the element wire a_r;e not adher ed, many of damages including stress or heat applied "to a cable c an be relaxed by the covering mater ial layer, and the dama. ge applied to the element wire can b> e reduced . Therefore, t he loose type covering can preferabl y/ be used depending on t he purpose of use . Regarding propagation of moisture , t he propagation of moi sture from the edge can be prevented by filling gel-like semisolids or graniαlar materials in the spac es , and by additional ly making thos e semisolids or granul_ ar materials have a function differen-t from moisture propagati on prevention, such as heat resistance , improvement in mechanical performance , or the like , covering having high performance can be formed. To produce the loose t^/pe covering, a space lay^er can be formed by controlling the extrusion a ni pple positi on at a cross head die and adjusting a pressure red-ucing device . Thickness of the space layer can be adj usted by thickness of the nipple and by pressuring or p xessure-reduc ing the space layer .

If necessary, a further covering layer ( secondary- covering layer) may be provided on the outer circumference of the covering layer (primary covering layer) . The secondary covering layer may contain a flame; retardant, a_n ultravioLet absorber, an antiox idant , a radical trapping agent , a quencher, a lubricant and the like . Those can also be introduced into

the primary covering layer so long as moisture-prroof performance is satisfied . The fILame retardant include a resin or additive containing a halogen such as bromin e , and a material containing phosphor . It is a main trend to add a. metal hydroxide as the flame reta rdant from the standpoint ozE safety such as toxic gas reduction . The metal h hydroxide has moisture as water of crystallization in the inside thereof , and deposited water In the course off production of the same ca nnot be removed completely . Therefore , it is desirable that a. flame retardant covering by the metal hydroxide ±s provided a s an outer layer cover ( secondary covering layer ) of the moistur e-proof covering (primary covering "
layer) of the I nvention . Further, to impart plural functions , a cover havi ng various f unctions may be laminated . For example, other t han the flame retardant as in the invention, a. barrier layer for suppr essing moisture absorption of an element wire o x a hygroscopic material for removing moisture , such as a hydroscopic tape or a hygroscopic gel , can be provided in the covering layer or between the covering layers , or a buffer layer such as a f iexible material layer or a foamed layer, for relaxing stres s when bending, a reinforcing layer? for increasing- rigidity, and the like ca n be selected and prov ided, depending- on the purpose of use . Wtiere the thermoplastic resin contain s , other than resins , a wire material such as a. fiber having high elastic mo dulus ( so-calLled high strength fib er ) and/or a metal wire having high rigidity, and the like as a structural material , dynamic strength of a cable obtained can be reinfo xced, which is preferable . Examples of the high strength .fiber include aramid fibers , polyester fibers and polyamide ff.ibers . Examples of the metal wire include stainless steel wires , zinc alloy wires and copper wires . However, the invention is not limited to those exampZLes . In addition, an outer sheath -ma.de of a metaH pipe for cable protection, a supporting wire for overhead cab> le construction, and a mechanism for improving workability wh_ en wiring cam be

incorporated.

The cable may have any desir-ed shape, depending on its use embodiment. For example, a. bundle cable formed by concentrically bundling element wires, a tape cabILe formed by aligning them in l±nes, a covered cable formed by covering them witti a presser coat or a wrapping sheath may Doe employed depending on the use of the cable .

As compared with the conventional optical fiber, the cable using the optical fiber of the invention has a broader latitude in axis sriif ting, and there fore, it may be butt- jointed. Preferably, however, an optical connector for joint is disposed at "the end of the cable, and the cables are sureILy fixed and connected via the optical connector therebetween. The connector can util ±ze any known and commercially-available one, such as PN connectors, SMA connectors, SMI connectors, F05 connectors, MU connectors, FC connectors and SC connectors.

The system for transmitting- optical signal using the opt ±cal fiber of the invention is constituted off an optical signal processor containing various optical members such as light emitter, light receiver, ligrit switch, optical isolator, opt ±cal integrated circuit, and optical transmit-receive module, ϊn this case, the optical fiber of the invention may be combined with any other optical fibers, and any known techniques relat±ng to it may be employed. For example, reference may be made to Base and Practice of Plastic Optical Fib>ers (issued by NTS) ; and Nikkei Electronics 20Ol .12.3 , pp. 110 -127 "Optical Structure Mounted on Printed-Wiring Board, Now or Never" . Combined with various techniques disclosed in these references, the invention may be favorably applied to licjht-transmission systems suitable e to short-range appliances for- high-speed laxge-capacity data communication and control with no influence of electromagnet ic waves thereon, typically for- example, in-unit wiring for computers and various digital instruments, in-iαnit wiring for vehicles and ships, optical

linking for optical terminals to digital devices or digital devices to each other, ancd indoor or in — area optical LAN for houses, aparrtments, factories, offices,- hospitals, s chools.

The invention is des cribed. in more detail with reference to the following Examples, in which thie material used, its amount and ratio, the detai-ls of the treatment and the trreatment process may be suitably modified or changed not overstepping the sprit and the scope of the invention. Accordingly, the invention should not be limitatively interpreted' by the

Examples mentioned below. (Average molecular weight)

Average molecular weight of a copolymer was measured with a gel permeation chromatography (GPC) by dissolving a part of a copolymer obtained in tetrahydr ofuran (THF) . Number average molecular weight (Mn) of a copolymer in the invention is a value when a polystyrene was used as a standard sub stance.

Proportion (molar ratio) o f each monomer constituting a copolymer was determined by an integrated value of 1
H-NHMR. Aceton-dδ or THF-d 8
was used in the NMR analysis. Glass transition temperature (T<g)

A 200 μm thick polymer film was prepared from a powdery polymer after rep recipitation purification^ using a high temperature press machine, a film of 100 mm x 500 mm was cut off therefrom, and this cut piece was used a. s a test piece.

Using this "test piece, elastic modulus and tens ile strength at break -was measured at a tensile rate of 3 πnα/min and measurement temperature of 25°C with Terxsilon universal tester (part number RTC-1210A, a product of Orientec Co. ) . (Ref rractive index)

Using a refractometer (DR- M2, a product of ATAGO Co .) , refractive index of a film test piece prepared above was

measured at an observation wavelength of 589 nm and a measurement temperature of 25°C.

Using a spectrophotometer (a product of JASCO Co. ) , spectroscopic -reflectivity wa s measured in a wavelength regd_on of from 380 to 780 nm at an incident angle of 5°. In Table 1 shown after, it was expressed as a mirrorr surface average reflectivity of from 450 to 650 nm. (Pencil hardness evaluation)

An antiref lective film was moistened at a temperature of

25°C and a humzLdity of 60%RH for 2 hours, and pencil hardness evaluation was conducted according to JIS K5400. (Mar resistance test)

Film surface was rubbed "with steel wool #0000 under a load of 200 g 10 times, and level of mar generated was confirmed. Judgment was according to the following criteria.

Entirely no mar : ®

Slight mar : O

Remarkable fine mar : δ

Remarkable mar : x

(Fingerprint adhesion evaluation)

It was employed as a measure of staining resistance of surface. An optical material, was moistened at a temperature of 25°C and a humidity of 60%RH for 2 hours, fingerprints was attached to a sample surface. The state when wiping off the fingerprints -with a cleaning cloth was observed, a_nd fingerprint adlhesion was evalLuated.

particles in a low refractive index layer, a sample was placed on a black paper, and was irradiated with diffus ±on while light directly overhead a_t a distance of 50 cm. State of scattering unevenness of the sample was observed, and the following evaluation was made.

No unevenness and observed uniformly : O

Scattering unevenness of "white color is observed on a part of sample : δ

Subsequently, 32.0 g (0. 316 mol) of tiriethylamine was added dropwise while maintaining the inner temperature at 10°C or lower, f o llowed by stirring at room tempe.rature for 1 h, our . THF was distilled off underr reduced pressure, and 1-50 ml of dichlorornethane was added, and then again ice cooled. 55 g

(0.37 mol ) of 2, 2, 3, 3, 3-pentaf luoropropsnol was added , and 37.6 g (0.37 mol) of triethylamine was added dropwi se while maintaining the inner temperature at 10 0
C or lower, followed by stirr-ing at room temperature for 1 hour. 150 ml of dichlorornethane and 0.5 liter of 2N EiCl were added to the reaction liquid to separate. An aqueous layer was removed, and an organ±c phase was washed with a saturated sodium chloride aqueous solution two times. The soILution was drried with anhydrous sodium sulfate, and a solvent was distilled off under reduced pressure. 1.1 g (0.013 mol) oiC morpholine was added thereto, and stirred under nitrogen atmosphere for 1 ..5 hours. A crude product was purified with a silica gel chromatography

4.8O g (0.200 mol) of sodium hydride (a product of ALdrich, dry 95%) and 40 ml of dehydrated THF were placed in a 200 ml three-necked flask (hereinafter, the. operation until the completion of stirring at temperature for 1 hour was conducted under nitrogen atmosphere), and ice cooled. While stiLrring, 60 ml of dehydrated THF solution of 3 "
7.2 g (0.221 rrxol) of hexafluoroisopropyl alcohol was added dropwise while maintaining a liquid temperature at 15°C or lower, followed by stirring at room temperature for 1 hourr .

This mixture was added to 200 ml of an ice cooILed THF solution of 17.6 g (0.179 mol) of maleic anhydride while stirring under nitrogen atmosphere and maintaining the inner temperature at 15°C or lower. After stirring at room temperature for 2 hours, the solution was poured in an ice-cooled IN hydrochloric acid, and extracted with diisopropyl alco-hol. An organic phase was washed wd_th a saturated sodium chloride aqueous solution two times, and dried with anhydrous sodium sulfate. A sol-vent was distill- ed off under reduced pressure. A crude product was purified by recrystallization in hexane to obtain 33.2 g (62%) of a while solid (3 — 8A) .

A mixture of 20 g (0.075 mol) of (3-8A), 10.7 g (0.090 mol) of thionyl chloride and 0.2 g of dimethylf ormamide (DMF) was stirred at 80°C for 2 hour. After ices-cooling the reaction liquid, 120 ml of acetonitrile and 7 .52 g (0.075 ml) of trif luoroethanol were added, and while maintaining the inner temperature at 15 C
C or lower, 7.6Og (0.075 mol) of trieth^/lamine was sdded dropwise, followed by stirring at room temperature for 1 hour. Ethyl acetate and diluted rxydrochloric acid were added to the reaction liquid to separate. An organic ph.ase was washed with a saturated sodium chloride aqueous solution two times. The solution was dried with anhydrous sodium sulfate, and a solvent was distilled off under reduced pressure. A crude product was purified with a silica gel chromatography (AcOEt/Hexane=l/30) , and then distilled "under reduced pressure

2, 2-azobis (2-methylpropionate) were added to the test tube, f ollowed by light shaking for mixing. After argon substitution, the test tube was sealed, with a silicone plug, and was aXlowed to stand at 65°C for 24 hours to conduct polymerization . The test tube was broken to obtain a rod-shaped polymer therefrom. The polymer was dissolved in THF, and tlhe resulting solution was poured in methanol to conduct repre cipitation. A powder obtained was again dissolved in THF, and the resulting soILution was poured in methanol to again conduct reprecipitation, followed by drying under reduced pressure, thereby obtaining 4.33 ςj (72%) of a whiJ_e powder. Compositional ratio (molar ratio) calculated from the integration va -lue of 1
H-NMR was (3-1) 45% and (4-1) 55%. Molecular weight was measured withi GPC. Number? average molecular weight was 177, 000, and mass average molecular weight was 352,000.

This copolymer had Tg of 94°C, and a refractive index of 1.414.

This copolymer was dissolved in T-HF, and the resuxlting

solution was applied to a slide glass. Tine resulting costing was heated to evaporate THF. A film thus obtained! was completely "transparent. Strength of a. film prepared using a high temperature press macriine was measured with Tensilon.. As a result, the copolymer had elastic modulus of 1, 650 MPa , and tensile strength of 34.7 MPa. Further, tine copolymer had low hygroscopic property sufficient to use as an optical member. [Example 1-2] Synthesis of Copolymer P-I —2

Synthesis was conducted by using (3-2) as a monomer in place of (3 —1) .

Monomer (3-2) was synthesized in the same manner as (3-1) of Monomer Synthesis Example 1.

Polymerization was conducted in the same manner ss in Example 1-1, except for using (3-2) in an equimolar amount in place of (3 — 1) . Reprecipi ~
tation operation was conducted two times in the same manner as in Example 1 — 1 to obtain a -while powder in a. yield 63%. Compositional ratio (molar ratio) calculated from the integration value of 11
H-NMR was (3-2 ) 42% and (4-1) 58%. Molecular weight was measured with GPC. Number average molecular weight was 205,000, and mass average molecular weight was 354,000.

This copolymer had Tg of 104 0
C, and a refractive .index of 1.417.

This copolymer was dissolved in THF, and the resulting solution was applied to a slide glass. Tine resulting coating was heated to evaporate THF. A film thus obtained was completely "transparent. Strength of a fd_lm prepared using a high temperature press macrαine was measured with Tensilon.. As a result, trie copolymer haci elastic modulus of 1,710 MPa , and tensile strength of 37.3 MPa. [Example 1-3] Synthesis of Copolymer P-I —5

Synthesis was conducted in the same manner as in Example 1-1, except for using (3-8) in an amount equimolar with (3-1) in place of (3-1) . Monomer: (3-8) used was one obtained by the

method described in Monomer Synthesis Example 2. Reprecipitat ion operation was conducted two times in the same manner as in Example 1-1 to obtain a while powder in a yield 63%. Compositional ratio (molar ratio) calculated from the integration value of 1
H-NMR was (3-8) 44% and (4-1) 56%. Molecular weight was measured with GPC. Number average molecular weight was 115, 000 , and mass averrage molecular weight was 234,000.

This copolymer had Tg- of 104 0
C, and a refractive index of 1.377.

This copolymer was d-Lssolved in THF, and the resulting solution was applied to a slide glass. Txie resulting coating was heated to evaporate THF. A film thus obtained was completely transparent. Strength of a film prepared using a high temperature press machine was measured with Tensilon. As a result, the copolymer had elastic modul_us of 1,200 MPa, and tensile strength of 29.0 M-Pa. [Comparative Example 1-1] Synthesis of Copolymer R-I of Dicyclohexyl fumarate and (4-1)

Dicyclohexyl fumarate was synthesized in the same manner as In (3-1) of Monomer Synthesis Example 1.

Polymerization was conducted in the same manner as in Example 1-1, except: for using di cyclohexyl fuaarate in an amount equimolar with (3-1) . Reprecipitation operation was conducted two times in the same manner as in Example 1-1 to obtain a wϊiile powder in a yield 68%. Molecular weight was measured with GPC. NumJoer average molecular weigrxt was 102,000, and mass ave rage molecular weight was 290,000.

This copolymer had Tg o ± 143°C.

Strength of a film prepared using a high "temperature p ress machine was measurred with Tensi_ Ion. As a resmlt, the copol ymer had elastic modulus of 1,220 MPa, and tensile strength of 10.5 MPa- .

Polymerization was conducted in the same manner a. s in Example 1-1, except for using ( 3-2) in an amomnt equimolar with (3 — 1) in place of (3-1), andvinyl acetate in an amount equiiaolar with (4-1) in place of (4-1) . Vinyl acetate was used by distilling a commercially available reagent, a product of Wako

Pure Chemical Industries, Ltd.

Reprecipitation operration was conducted two times in the same manner as in Example 1 —1 to obtain a while powder in a yield 70%. Molecular weight was measured with GPC. Numbe JC average molecular weight was 53, OO 0, and mass average molecul ar weight was 346,000. It was seen that the molecu IL ar weight distribution is wide as compared with P-l-1.

This copolymer had Tg of 65 0
C.

Strength of a film prepared using a. high temperature press machine was measured with Tensilon. As a result, the copolymer had elastic modulus of 1,280 MPa, and tensile strength of 16.9 MPa.

Measurement results relating to p>olymers synthesized in Examples 1-H to 1-3 and Comparative Exa.mples 1 and 2 are shown in Table 1.

It is apparent that the polyitierr of the invention has narrow molecular weight distribution (Mw/Mn is about 2 or less) , high Tg (90 0
C or higher), and excellent mechanical properties, particularly tensile strength.

copolymer solution obtained was directly poiαred in hexane, and reprecipit ation purification was conducted two times to obtain 39.1 g of a f luorine-containing copolymer. The copolymer obtained had Tg of 102°C, a weight average mol ecular weight (Mw) of 58,000 and a refractive index of 1.385.

[Example 2-2]

Synthesis of Fluorine-containing Copolymer P-2-24 Having

Hydroxyl Group at Side Chain

Exarαple 2-1 was followed, except for changing (3-2) to

(3-1) in an amount equimolar with (3-2), to obtain 30.2 cj of a copolymer as a while powder. The copolymer obtained hacd Tg of 94°C, a weight average molecular weight (Mw) of 66,000 and a refractive index of 1.416.

[Example 2-3] Preparation of Cured Film

1.5 g of a methoxylated methylmelamine, SYMEL 303, a product of Mitsui Cytec Co. , as a curing agent was added to 100 g of MEK solution of 10 mass% of (P-2-22) obtained in Example 2-1, and heat reaction treatment was conducted at 70°C for 5 hours. 0.1 g of p-tolynenesulf onic acid as a curing catalyst was added "
to the reaction mixture to prepare a low refractive index layer forming composition.

This low refractive index layer forming composition was diluted to a solid content of 6mass%, and the ^resulting solution was applied to a substrate comprising a support (TAC, a product of Fuji Photo Film Co. ) having formed thereon a hard coat layer

(refractive index: 1.53) using a wire bar coater (#3) . The resulting coating was heated at 120°C for 60 minutes to form a cured film of 100 nm. Trie evaluation results are shown in Table 2.

[Example 2-4] Preparation of Cured Film

A cured film was .formed in the same manner as in Example 2-3, except for changing (P- 2-22) to the same amount of (P-2— 24) .

The evaluation results are shown in Table 1 .

[Comparative Example 2-1 ]

A low refr active index layer forming compo sition was prepared in the same manner as in Example 2-3 de scribed in JP-A-11-228631 , and using this composition, a cured film was formed in the same manner as in Example 2-3 . The evaluation results are shown in Table 2 .

[Example 2 -5 ]

Fluorine-Containing Copolymer Having MethacryloyIL Group at

Side Chain

20 g of the copolymer (P-2-22) obtained in Example 2-1 was dissolved in 100 ml of N,N-diemthyl acetamine ^
and after adding dropwise 5.0 g of methacitryloyl chloride (a product of Wako Pure Chemical Indsutries, Ltd.) under ice cooling, the resulting mixture was stirred at xoom temperature for 10 hours. The mixture was extracted with ethyl acetate, and an organic phase was washed with water, and concentrated. Hexane was added for reprecipitatdLon. The precipitate was further dissolved in THF, and reprecipitated with hexane, thereby obtaining 13 g of a fluorine-containing copolymer as a while po-wder. The copolymer had a weight average molecular weight (Mw) of 64,000, and a refractive index of 1.392.

[Example 2-6]

Fluorine-Containing Copolymer Having Methacryloyl Group at

Side Chain

A fluorine — containing cop olymer was synthes ized in the same manner as in Example 2-5, except for changing ( P-2-22 ) to the same weight of ( P-2-24) , "thereby obtaining 13 g of a copolymer (while powder) . The copolymer had a wei ght average molecular weight (Mw) of 61, 00 0 , and a refractive index of 1 . 421 .

[Example 2-7 ]

0 . 5 g of Irgacure 907 ( a product of Ciba Giegy) as a photopolymerization initiator was added to 100 g of MEK solution

of 10 mass% of the copolymer obtained in Example 2-5 to obtain a low refractive index layer forπi-Lng composition.

This low ref Jtractive index layer forming composition was diluted to a solid content of 6 mass% , and applied to a substrate comprising TAC having formed thereon a hard coat layer

( ..refractive index: 1.53) having a thickness of 5 μm using a wire bar coater (#3), followed by drying "
at 80°C for 1 minute. The resulting coating film was irradiated with ultraviolet rays under nitrogen atmosphere to form a cured film. The evaluation results are shown in Table 2.

[Example 2-8]

A cured film was formed in the same manner as in Example 2 — 7, except for changing the copolymer used to the copolymer obtained in Example 2-6. The evaluation results are shown in Table 1.

[Comparative Example 2-2]

A low refractive index laye_r forming compositiLon was prepared in the same manner as in Reference Example 11 described in Patent No. 3498381, and using the composition, a cured film was formed in the same manner as in Example 2-7. The evaluation results are shown in Table 2.

[Example 3-1]

Production Example of Optical Fiber (S-I) by Intenrf acial Gel

Polymerization Using Polymer (P-l — 4)

A hollow tube (one end was sealed with the same resin) havj_ng a thickness of 1 mm, an inner diameter of 22 mm and a length of 30 cm made of a polyλrinylidene fluoride resin

(refractive index: 1_.38), previousl y prepared by melt extrusion molding was inserted in a stainless steel pipe, and was set to a rotation polymerization apparatus. Moisture, a polymerization inhibitor, (3-3) from which dusts were sufficiently removed, the equimolar (4-1) , and 0.24% (weight rat-Lo to the sum of monomers) of dimethyl

2,2 λ
-azobisisobutynrate as a polymerization initiator were poured in the tube, and after substituting with nitrogen, the

tube was in a sealed state. While rotating the pipe, polymerization was conducted at 65°C for 3 hours, 70°C for 2 hours, and 90°C for 12 hours, to prepare an outer core portion (corresponding to an outermost layer ) having a thickness of 4 mm.

Polymerization of an inner core portion was conducted as follows . The hollow tube having the outer core portion prepared was vertically placed in a pressurre polymerization vessel heated to 80 0
C. (3-3) and (4-1) in equimolar amounts, and bromobenzene as a doptant were added so as to be an amount of 5% to the total weight of the monomer" s. 0.3% (weigtit ratio to the sum of the monomers) of di-tert-butyl peroxide as a polymeri zation initiator was added,, followed by sufficient deaeration. The polymeri zable composition heated to 80°C was gently added to a hoILlow portion off the hollow tube. After substituting the inside of the pressure polymerization vessel with a nitrogen atmosphere, pressure was applied up to 0.2 MPa, and heat polymerization was conducted at 100°C for: 48 hours. While maintaining the pressured state, heat polymerization and heat treatment were conducted at 14O°C for 24 hours to obtain a preform.

The preform obtained above was melt stretched. The preform ■
was inserted in a heating furrnace controlled to 200 to

240 0
C vertically downwardly. Stretching rate was controlled according to a diameter of a fiber measured throuαgh a fiber diameter- measurement device so as to Ifoe the desired zfiber outer diameter (300 μm) . Trie fiber was primarily covered with a low density polyethylene, and then secondarily covered with a covering material comprising magnesium hydroxide kneaded with a nitrϋe butadiene xubber and a polyethylene. Refractive index in the sectional direction of the optical fiioer preform was that a clad portion is 1.380 being constant, aa outer core portion is 1.417 being constant, and an inner core portion is from 1.417 to 1.426 C central portion) . The refractive index

Transmission loss of the covered fiber obtained, and loss increase before and after placing the covered fiber in an atmosphere at 75°C and 8O% relative humidity for 24O hours are shown in Table 3.

[Example 3-2]

Production Example of Optical Fiber (S-2) Using (P-l-5)

A covered fiber was prepared in the same mariner as in Example 3 — 1, except for changing the monomer used from (3-3) to (3-8) . Refractive index in the sectional direction of the optical fiber preform wss that a clad portion is 1 .380 being constant, an outer core portion is 1 .390 being constant, and an inner core portion is from 1.390 to 1.401 (central, portion) . The refractive index distribution of tlhe inner core portion drew an upwardly convex parabola.

Transmission loss of the covered, fiber obtained, and loss increase before and after placing the covered fiber in an atmosphere at 75°C and 8 O% relative hnαmidity for 24O hours are shown in Table 3. The evaluation results are suirunarized in Table 3.

[Comparative Example 3—1]

Production Example of Optical Fiber: (R-I) Using Polymethyl Methacrylste (PMMA)

A covered fiber was prepared in the same manner as in Example 3 — 1, except for changing the monomer used to 3MMA (methyl methacrylste) and changing the dopant from bromobenzene to diphneyl sulfide (5% in weight ratio to MMA) . The evaluation results axe summarized in Table -3.

Table 3

Transmission loss and loss increase value: 650 nm light source

INDUSTRIAL APPLICABILITY OF THE INVENTION

The copolymer of the invention has excellent transparency, has low hygroscopic property originated from fluorine atom, maintain heat resistance due to 1,2-diester structure, and gives good mechanical strength.

The copolymer of the invention and the curing resin composition containing the copolymer forms a good cured film having a sufficient low ref lectivity, and the cured film has low refractive index and has excellent mar resistance. Therefore, the copolymer of the invention and t he curing resin composition containing the copolymer can particularly advantageously be used for the formation of optical materials such as an antiref lective film and an optical fiber clad material . Further, utilizing high fluorine content, those can suitably be used as paint materials to a substrate requiring weather resistance, weather-resistant film materials, coating materials , and the Like. Further, the cured fil m has excellent adhesion to a substrate, in addition to low refractive index and excellent mar resistance, and gives good antireflective

effect. Therefore, such a cured film is particularly useful as an antireflective film, and by applying tb_e film to various displays, its visibility can b>e improved.

Additionally, the optica.1 waveguide of the invention, particularly optical fibers (POF) , is flexible and has low transmission loss by using, as its raw material, a polymer having good low hygroscopic prroperty (moisture resistance) , heat resistance ( high Tg) , mechanical strength (elastic modulus and. tensile strength) and transparency, and capable of being easily produced.